Merge branch 'master' into url_engine_problem

.github/CODEOWNERS

@@ -0,0 +1,3 @@
+dbms/* @ClickHouse/core-assigner
+docs/* @ClickHouse/docs
+docs/zh/* @ClickHouse/docs-zh

.github/labeler.keywords.yml

@@ -1 +0,0 @@
-pr-feature: "New Feature"

.github/labeler.yml

@@ -1,23 +0,0 @@
-# Build changes
-pr-build:
-  - "**/CMakeLists.txt"
-
-# Documentation PRs
-documentation:
-  - "**/*.md"
-  - "docs/**/*"
-pr-documentation:
-  - "**/*.md"
-  - "docs/**/*"
-
-# Component labels
-comp-mutations:
-  - "**/*Mutation*"
-comp-matview:
-  - "**/*MaterializedView*"
-comp-skipidx:
-  - "**/*Indices*"
-comp-kafka:
-  - "dbms/src/Storages/Kafka/**/*"
-  - "dbms/tests/integration/test_storage_kafka/**/*"
-  - "utils/kafka/**/*"

.github/stale.yml

@@ -1,7 +1,7 @@
 # Configuration for probot-stale - https://github.com/probot/stale
 
 # Number of days of inactivity before an Issue or Pull Request becomes stale
-daysUntilStale: 45
+daysUntilStale: 60
 
 # Number of days of inactivity before an Issue or Pull Request with the stale label is closed.
 # Set to false to disable. If disabled, issues still need to be closed manually, but will remain marked as stale.
@@ -21,6 +21,8 @@ exemptLabels:
   - st-accepted
   - st-in-progress
   - st-waiting-for-fix
+  - segfault
+  - crash
 
 # Set to true to ignore issues in a project (defaults to false)
 exemptProjects: false
@@ -37,8 +39,8 @@ staleLabel: stale
 # Comment to post when marking as stale. Set to `false` to disable
 markComment: >
   This issue has been automatically marked as stale because it has not had
-  recent activity. It will be closed if no further activity occurs. Thank you
-  for your contributions.
+  recent activity. Please post a comment if this issue is still relevant to you.
+  Thank you for your contributions.
 
 # Comment to post when removing the stale label.
 # unmarkComment: >
@@ -57,10 +59,11 @@ limitPerRun: 30
 # Optionally, specify configuration settings that are specific to just 'issues' or 'pulls':
 pulls:
   daysUntilStale: 365
+  daysUntilClose: 60
   markComment: >
     This pull request has been automatically marked as stale because it has not had
-    any activity for over a year. It will be closed if no further activity occurs. Thank you
-    for your contributions.
+    any activity for over a year. Please post a comment about whether you intend to continue working on it.
+    Thank you for your contributions.
 
 # issues:
 #   exemptLabels:

.github/workflows/labeler.yml

@@ -1,11 +0,0 @@
-name: "Pull Request Labeler"
-on:
-  pull_request
-
-jobs:
-  by-filename:
-    runs-on: ubuntu-latest
-    steps:
-    - uses: "actions/labeler@v2"
-      with:
-        repo-token: "${{ secrets.GITHUB_TOKEN }}"

README.md

@@ -13,8 +13,9 @@ ClickHouse is an open-source column-oriented database management system that all
 * You can also [fill this form](https://forms.yandex.com/surveys/meet-yandex-clickhouse-team/) to meet Yandex ClickHouse team in person.
 
 ## Upcoming Events
-* [ClickHouse Meetup in Shanghai](https://www.huodongxing.com/event/4483760336000) on October 27.
 * [ClickHouse Meetup in Tokyo](https://clickhouse.connpass.com/event/147001/) on November 14.
 * [ClickHouse Meetup in Istanbul](https://www.eventbrite.com/e/clickhouse-meetup-istanbul-create-blazing-fast-experiences-w-clickhouse-tickets-73101120419) on November 19.
 * [ClickHouse Meetup in Ankara](https://www.eventbrite.com/e/clickhouse-meetup-ankara-create-blazing-fast-experiences-w-clickhouse-tickets-73100530655) on November 21.
 * [ClickHouse Meetup in Singapore](https://www.meetup.com/Singapore-Clickhouse-Meetup-Group/events/265085331/) on November 23.
+* [ClickHouse Meetup in San Francisco](https://www.eventbrite.com/e/clickhouse-december-meetup-registration-78642047481) on December 3.
+

cmake/dbms_glob_sources.cmake

@@ -1,13 +1,20 @@
-macro(add_glob cur_list)
-    file(GLOB __tmp RELATIVE ${CMAKE_CURRENT_SOURCE_DIR} ${ARGN})
-    list(APPEND ${cur_list} ${__tmp})
-endmacro()
+if (CMAKE_VERSION VERSION_GREATER_EQUAL "3.12")
+    macro(add_glob cur_list)
+        file(GLOB __tmp RELATIVE ${CMAKE_CURRENT_SOURCE_DIR} CONFIGURE_DEPENDS ${ARGN})
+        list(APPEND ${cur_list} ${__tmp})
+    endmacro()
+else ()
+    macro(add_glob cur_list)
+        file(GLOB __tmp RELATIVE ${CMAKE_CURRENT_SOURCE_DIR} ${ARGN})
+        list(APPEND ${cur_list} ${__tmp})
+    endmacro()
+endif ()
 
 macro(add_headers_and_sources prefix common_path)
-    add_glob(${prefix}_headers RELATIVE ${CMAKE_CURRENT_SOURCE_DIR} ${common_path}/*.h)
+    add_glob(${prefix}_headers ${CMAKE_CURRENT_SOURCE_DIR} ${common_path}/*.h)
     add_glob(${prefix}_sources ${common_path}/*.cpp ${common_path}/*.c ${common_path}/*.h)
 endmacro()
 
 macro(add_headers_only prefix common_path)
-    add_glob(${prefix}_headers RELATIVE ${CMAKE_CURRENT_SOURCE_DIR} ${common_path}/*.h)
+    add_glob(${prefix}_headers ${CMAKE_CURRENT_SOURCE_DIR} ${common_path}/*.h)
 endmacro()

contrib/CMakeLists.txt

@@ -124,7 +124,7 @@ if (USE_INTERNAL_SSL_LIBRARY)
     add_library(OpenSSL::SSL ALIAS ${OPENSSL_SSL_LIBRARY})
 endif ()
 
-if (ENABLE_MYSQL AND USE_INTERNAL_MYSQL_LIBRARY)
+function(mysql_support)
     set(CLIENT_PLUGIN_CACHING_SHA2_PASSWORD STATIC)
     set(CLIENT_PLUGIN_SHA256_PASSWORD STATIC)
     set(CLIENT_PLUGIN_REMOTE_IO OFF)
@@ -136,7 +136,15 @@ if (ENABLE_MYSQL AND USE_INTERNAL_MYSQL_LIBRARY)
     if (GLIBC_COMPATIBILITY)
         set(LIBM glibc-compatibility)
     endif()
+    if (USE_INTERNAL_ZLIB_LIBRARY)
+        set(ZLIB_FOUND ON)
+        set(ZLIB_LIBRARY zlibstatic)
+        set(WITH_EXTERNAL_ZLIB ON)
+    endif()
     add_subdirectory (mariadb-connector-c)
+endfunction()
+if (ENABLE_MYSQL AND USE_INTERNAL_MYSQL_LIBRARY)
+    mysql_support()
 endif ()
 
 if (USE_INTERNAL_RDKAFKA_LIBRARY)

dbms/CMakeLists.txt

@@ -130,8 +130,8 @@ list (APPEND dbms_headers
 
 list (APPEND dbms_sources src/TableFunctions/ITableFunction.cpp src/TableFunctions/TableFunctionFactory.cpp)
 list (APPEND dbms_headers src/TableFunctions/ITableFunction.h   src/TableFunctions/TableFunctionFactory.h)
-list (APPEND dbms_sources src/Dictionaries/DictionaryFactory.cpp src/Dictionaries/DictionarySourceFactory.cpp src/Dictionaries/DictionaryStructure.cpp)
-list (APPEND dbms_headers src/Dictionaries/DictionaryFactory.h   src/Dictionaries/DictionarySourceFactory.h   src/Dictionaries/DictionaryStructure.h)
+list (APPEND dbms_sources src/Dictionaries/DictionaryFactory.cpp src/Dictionaries/DictionarySourceFactory.cpp src/Dictionaries/DictionaryStructure.cpp  src/Dictionaries/getDictionaryConfigurationFromAST.cpp)
+list (APPEND dbms_headers src/Dictionaries/DictionaryFactory.h   src/Dictionaries/DictionarySourceFactory.h   src/Dictionaries/DictionaryStructure.h src/Dictionaries/getDictionaryConfigurationFromAST.h)
 
 if (NOT ENABLE_SSL)
     list (REMOVE_ITEM clickhouse_common_io_sources src/Common/OpenSSLHelpers.cpp)
@@ -153,12 +153,10 @@ add_subdirectory(src/Common/Config)
 set (all_modules)
 macro(add_object_library name common_path)
     if (MAKE_STATIC_LIBRARIES OR NOT SPLIT_SHARED_LIBRARIES)
-        add_glob(dbms_headers RELATIVE ${CMAKE_CURRENT_SOURCE_DIR} ${common_path}/*.h)
-        add_glob(dbms_sources ${common_path}/*.cpp ${common_path}/*.c ${common_path}/*.h)
+        add_headers_and_sources(dbms ${common_path})
     else ()
         list (APPEND all_modules ${name})
-        add_glob(${name}_headers RELATIVE ${CMAKE_CURRENT_SOURCE_DIR} ${common_path}/*.h)
-        add_glob(${name}_sources ${common_path}/*.cpp ${common_path}/*.c ${common_path}/*.h)
+        add_headers_and_sources(${name} ${common_path})
         add_library(${name} SHARED ${${name}_sources} ${${name}_headers})
         target_link_libraries (${name} PRIVATE -Wl,--unresolved-symbols=ignore-all)
     endif ()

dbms/cmake/version.cmake

@@ -1,11 +1,11 @@
 # This strings autochanged from release_lib.sh:
-set(VERSION_REVISION 54427)
+set(VERSION_REVISION 54428)
 set(VERSION_MAJOR 19)
-set(VERSION_MINOR 16)
+set(VERSION_MINOR 17)
 set(VERSION_PATCH 1)
-set(VERSION_GITHASH 38f65a6a2120d2e76bcf71131068f41195149dfc)
-set(VERSION_DESCRIBE v19.16.1.1-prestable)
-set(VERSION_STRING 19.16.1.1)
+set(VERSION_GITHASH 5286d0afb285a5fbf3d320af3daa6de6b1841374)
+set(VERSION_DESCRIBE v19.17.1.1-prestable)
+set(VERSION_STRING 19.17.1.1)
 # end of autochange
 
 set(VERSION_EXTRA "" CACHE STRING "")

dbms/programs/benchmark/Benchmark.cpp

@@ -365,7 +365,7 @@ private:
         Stopwatch watch;
         RemoteBlockInputStream stream(
             *(*connection_entries[connection_index]),
-            query, {}, global_context, &settings, nullptr, Tables(), query_processing_stage);
+            query, {}, global_context, &settings, nullptr, Scalars(), Tables(), query_processing_stage);
 
         Progress progress;
         stream.setProgressCallback([&progress](const Progress & value) { progress.incrementPiecewiseAtomically(value); });

dbms/programs/odbc-bridge/ColumnInfoHandler.cpp

@@ -19,6 +19,7 @@
 #include <Poco/Net/HTTPServerResponse.h>
 #include <Poco/Net/HTMLForm.h>
 #include <DataTypes/DataTypeFactory.h>
+#include <DataTypes/DataTypeNullable.h>
 #include <IO/WriteBufferFromHTTPServerResponse.h>
 #include <IO/WriteHelpers.h>
 #include <Parsers/ParserQueryWithOutput.h>
@@ -37,12 +38,16 @@ namespace
 
         switch (type)
         {
+            case SQL_TINYINT:
+                return factory.get("Int8");
             case SQL_INTEGER:
                 return factory.get("Int32");
             case SQL_SMALLINT:
                 return factory.get("Int16");
+            case SQL_BIGINT:
+                return factory.get("Int64");
             case SQL_FLOAT:
-                return factory.get("Float32");
+                return factory.get("Float64");
             case SQL_REAL:
                 return factory.get("Float32");
             case SQL_DOUBLE:
@@ -154,9 +159,19 @@ void ODBCColumnsInfoHandler::handleRequest(Poco::Net::HTTPServerRequest & reques
             SQLSMALLINT type = 0;
             /// TODO Why 301?
             SQLCHAR column_name[301];
-            /// TODO Result is not checked.
-            POCO_SQL_ODBC_CLASS::SQLDescribeCol(hstmt, ncol, column_name, sizeof(column_name), nullptr, &type, nullptr, nullptr, nullptr);
-            columns.emplace_back(reinterpret_cast<char *>(column_name), getDataType(type));
+
+            SQLSMALLINT nullable;
+            const auto result = POCO_SQL_ODBC_CLASS::SQLDescribeCol(hstmt, ncol, column_name, sizeof(column_name), nullptr, &type, nullptr, nullptr, &nullable);
+            if (POCO_SQL_ODBC_CLASS::Utility::isError(result))
+                throw POCO_SQL_ODBC_CLASS::StatementException(hstmt);
+
+            auto column_type = getDataType(type);
+            if (nullable == SQL_NULLABLE)
+            {
+                column_type = std::make_shared<DataTypeNullable>(column_type);
+            }
+
+            columns.emplace_back(reinterpret_cast<char *>(column_name), std::move(column_type));
         }
 
         WriteBufferFromHTTPServerResponse out(request, response, keep_alive_timeout);

dbms/programs/server/ReplicasStatusHandler.cpp

@@ -44,7 +44,7 @@ void ReplicasStatusHandler::handleRequest(Poco::Net::HTTPServerRequest & request
             if (db.second->getEngineName() == "Lazy")
                 continue;
 
-            for (auto iterator = db.second->getIterator(context); iterator->isValid(); iterator->next())
+            for (auto iterator = db.second->getTablesIterator(context); iterator->isValid(); iterator->next())
             {
                 auto & table = iterator->table();
                 StorageReplicatedMergeTree * table_replicated = dynamic_cast<StorageReplicatedMergeTree *>(table.get());

dbms/programs/server/Server.cpp

@@ -37,10 +37,12 @@
 #include <Interpreters/AsynchronousMetrics.h>
 #include <Interpreters/DDLWorker.h>
 #include <Interpreters/ExternalDictionariesLoader.h>
+#include <Interpreters/ExternalModelsLoader.h>
 #include <Interpreters/ProcessList.h>
 #include <Interpreters/loadMetadata.h>
 #include <Interpreters/DNSCacheUpdater.h>
 #include <Interpreters/SystemLog.cpp>
+#include <Interpreters/ExternalLoaderXMLConfigRepository.h>
 #include <Storages/StorageReplicatedMergeTree.h>
 #include <Storages/System/attachSystemTables.h>
 #include <AggregateFunctions/registerAggregateFunctions.h>
@@ -922,6 +924,12 @@ int Server::main(const std::vector<std::string> & /*args*/)
                 global_context->tryCreateEmbeddedDictionaries();
                 global_context->getExternalDictionariesLoader().enableAlwaysLoadEverything(true);
             }
+
+            auto dictionaries_repository = std::make_unique<ExternalLoaderXMLConfigRepository>(config(), "dictionaries_config");
+            global_context->getExternalDictionariesLoader().addConfigRepository("", std::move(dictionaries_repository));
+
+            auto models_repository = std::make_unique<ExternalLoaderXMLConfigRepository>(config(), "models_config");
+            global_context->getExternalModelsLoader().addConfigRepository("", std::move(models_repository));
         }
         catch (...)
         {

dbms/programs/server/TCPHandler.cpp

@@ -850,9 +850,10 @@ bool TCPHandler::receivePacket()
             return true;
 
         case Protocol::Client::Data:
+        case Protocol::Client::Scalar:
             if (state.empty())
                 receiveUnexpectedData();
-            return receiveData();
+            return receiveData(packet_type == Protocol::Client::Scalar);
 
         case Protocol::Client::Ping:
             writeVarUInt(Protocol::Server::Pong, *out);
@@ -957,39 +958,44 @@ void TCPHandler::receiveUnexpectedQuery()
     throw NetException("Unexpected packet Query received from client", ErrorCodes::UNEXPECTED_PACKET_FROM_CLIENT);
 }
 
-bool TCPHandler::receiveData()
+bool TCPHandler::receiveData(bool scalar)
 {
     initBlockInput();
 
     /// The name of the temporary table for writing data, default to empty string
-    String external_table_name;
-    readStringBinary(external_table_name, *in);
+    String name;
+    readStringBinary(name, *in);
 
     /// Read one block from the network and write it down
     Block block = state.block_in->read();
 
     if (block)
     {
-        /// If there is an insert request, then the data should be written directly to `state.io.out`.
-        /// Otherwise, we write the blocks in the temporary `external_table_name` table.
-        if (!state.need_receive_data_for_insert && !state.need_receive_data_for_input)
-        {
-            StoragePtr storage;
-            /// If such a table does not exist, create it.
-            if (!(storage = query_context->tryGetExternalTable(external_table_name)))
-            {
-                NamesAndTypesList columns = block.getNamesAndTypesList();
-                storage = StorageMemory::create("_external", external_table_name, ColumnsDescription{columns}, ConstraintsDescription{});
-                storage->startup();
-                query_context->addExternalTable(external_table_name, storage);
-            }
-            /// The data will be written directly to the table.
-            state.io.out = storage->write(ASTPtr(), *query_context);
-        }
-        if (state.need_receive_data_for_input)
-            state.block_for_input = block;
+        if (scalar)
+            query_context->addScalar(name, block);
         else
-            state.io.out->write(block);
+        {
+            /// If there is an insert request, then the data should be written directly to `state.io.out`.
+            /// Otherwise, we write the blocks in the temporary `external_table_name` table.
+            if (!state.need_receive_data_for_insert && !state.need_receive_data_for_input)
+            {
+                StoragePtr storage;
+                /// If such a table does not exist, create it.
+                if (!(storage = query_context->tryGetExternalTable(name)))
+                {
+                    NamesAndTypesList columns = block.getNamesAndTypesList();
+                    storage = StorageMemory::create("_external", name, ColumnsDescription{columns}, ConstraintsDescription{});
+                    storage->startup();
+                    query_context->addExternalTable(name, storage);
+                }
+                /// The data will be written directly to the table.
+                state.io.out = storage->write(ASTPtr(), *query_context);
+            }
+            if (state.need_receive_data_for_input)
+                state.block_for_input = block;
+            else
+                state.io.out->write(block);
+        }
         return true;
     }
     else

dbms/programs/server/TCPHandler.h

@@ -153,7 +153,7 @@ private:
     void receiveHello();
     bool receivePacket();
     void receiveQuery();
-    bool receiveData();
+    bool receiveData(bool scalar);
     bool readDataNext(const size_t & poll_interval, const int & receive_timeout);
     void readData(const Settings & global_settings);
     std::tuple<size_t, int> getReadTimeouts(const Settings & global_settings);

dbms/programs/server/config.xml

@@ -199,7 +199,21 @@
                      <port>9000</port>
                  </replica>
              </shard>
-         </test_cluster_two_shards_localhost>
+        </test_cluster_two_shards_localhost>
+        <test_cluster_two_shards>
+            <shard>
+                <replica>
+                    <host>127.0.0.1</host>
+                    <port>9000</port>
+                </replica>
+            </shard>
+            <shard>
+                <replica>
+                    <host>127.0.0.2</host>
+                    <port>9000</port>
+                </replica>
+            </shard>
+        </test_cluster_two_shards>
         <test_shard_localhost_secure>
             <shard>
                 <replica>

dbms/src/AggregateFunctions/AggregateFunctionAvg.h

@@ -31,9 +31,9 @@ struct AggregateFunctionAvgData
             if constexpr (std::numeric_limits<ResultT>::is_iec559)
                 return static_cast<ResultT>(sum) / count; /// allow division by zero
 
-        if (!count)
-            throw Exception("AggregateFunctionAvg with zero values", ErrorCodes::LOGICAL_ERROR);
-        return static_cast<ResultT>(sum) / count;
+        if (count == 0)
+            return static_cast<ResultT>(0);
+        return static_cast<ResultT>(sum / count);
     }
 };
 
@@ -43,10 +43,10 @@ template <typename T, typename Data>
 class AggregateFunctionAvg final : public IAggregateFunctionDataHelper<Data, AggregateFunctionAvg<T, Data>>
 {
 public:
-    using ResultType = std::conditional_t<IsDecimalNumber<T>, Decimal128, Float64>;
-    using ResultDataType = std::conditional_t<IsDecimalNumber<T>, DataTypeDecimal<Decimal128>, DataTypeNumber<Float64>>;
+    using ResultType = std::conditional_t<IsDecimalNumber<T>, T, Float64>;
+    using ResultDataType = std::conditional_t<IsDecimalNumber<T>, DataTypeDecimal<T>, DataTypeNumber<Float64>>;
     using ColVecType = std::conditional_t<IsDecimalNumber<T>, ColumnDecimal<T>, ColumnVector<T>>;
-    using ColVecResult = std::conditional_t<IsDecimalNumber<T>, ColumnDecimal<Decimal128>, ColumnVector<Float64>>;
+    using ColVecResult = std::conditional_t<IsDecimalNumber<T>, ColumnDecimal<T>, ColumnVector<Float64>>;
 
     /// ctor for native types
     AggregateFunctionAvg(const DataTypes & argument_types_)

dbms/src/AggregateFunctions/ReservoirSampler.h

@@ -109,8 +109,11 @@ public:
     double quantileInterpolated(double level)
     {
         if (samples.empty())
+        {
+            if (DB::IsDecimalNumber<T>)
+                return 0;
             return onEmpty<double>();
-
+        }
         sortIfNeeded();
 
         double index = std::max(0., std::min(samples.size() - 1., level * (samples.size() - 1)));

dbms/src/Client/Connection.cpp

@@ -30,6 +30,7 @@
 
 namespace CurrentMetrics
 {
+    extern const Metric SendScalars;
     extern const Metric SendExternalTables;
 }
 
@@ -441,7 +442,7 @@ void Connection::sendCancel()
 }
 
 
-void Connection::sendData(const Block & block, const String & name)
+void Connection::sendData(const Block & block, const String & name, bool scalar)
 {
     //LOG_TRACE(log_wrapper.get(), "Sending data");
 
@@ -455,7 +456,10 @@ void Connection::sendData(const Block & block, const String & name)
         block_out = std::make_shared<NativeBlockOutputStream>(*maybe_compressed_out, server_revision, block.cloneEmpty());
     }
 
-    writeVarUInt(Protocol::Client::Data, *out);
+    if (scalar)
+        writeVarUInt(Protocol::Client::Scalar, *out);
+    else
+        writeVarUInt(Protocol::Client::Data, *out);
     writeStringBinary(name, *out);
 
     size_t prev_bytes = out->count();
@@ -484,6 +488,44 @@ void Connection::sendPreparedData(ReadBuffer & input, size_t size, const String
 }
 
 
+void Connection::sendScalarsData(Scalars & data)
+{
+    if (data.empty())
+        return;
+
+    Stopwatch watch;
+    size_t out_bytes = out ? out->count() : 0;
+    size_t maybe_compressed_out_bytes = maybe_compressed_out ? maybe_compressed_out->count() : 0;
+    size_t rows = 0;
+
+    CurrentMetrics::Increment metric_increment{CurrentMetrics::SendScalars};
+
+    for (auto & elem : data)
+    {
+        rows += elem.second.rows();
+        sendData(elem.second, elem.first, true /* scalar */);
+    }
+
+    out_bytes = out->count() - out_bytes;
+    maybe_compressed_out_bytes = maybe_compressed_out->count() - maybe_compressed_out_bytes;
+    double elapsed = watch.elapsedSeconds();
+
+    std::stringstream msg;
+    msg << std::fixed << std::setprecision(3);
+    msg << "Sent data for " << data.size() << " scalars, total " << rows << " rows in " << elapsed << " sec., "
+        << static_cast<size_t>(rows / watch.elapsedSeconds()) << " rows/sec., "
+        << maybe_compressed_out_bytes / 1048576.0 << " MiB (" << maybe_compressed_out_bytes / 1048576.0 / watch.elapsedSeconds() << " MiB/sec.)";
+
+    if (compression == Protocol::Compression::Enable)
+        msg << ", compressed " << static_cast<double>(maybe_compressed_out_bytes) / out_bytes << " times to "
+            << out_bytes / 1048576.0 << " MiB (" << out_bytes / 1048576.0 / watch.elapsedSeconds() << " MiB/sec.)";
+    else
+        msg << ", no compression.";
+
+    LOG_DEBUG(log_wrapper.get(), msg.rdbuf());
+}
+
+
 void Connection::sendExternalTablesData(ExternalTablesData & data)
 {
     if (data.empty())

dbms/src/Client/Connection.h

@@ -133,7 +133,9 @@ public:
 
     void sendCancel();
     /// Send block of data; if name is specified, server will write it to external (temporary) table of that name.
-    void sendData(const Block & block, const String & name = "");
+    void sendData(const Block & block, const String & name = "", bool scalar = false);
+    /// Send all scalars.
+    void sendScalarsData(Scalars & data);
     /// Send all contents of external (temporary) tables.
     void sendExternalTablesData(ExternalTablesData & data);
 

dbms/src/Client/MultiplexedConnections.cpp

@@ -51,6 +51,21 @@ MultiplexedConnections::MultiplexedConnections(
     active_connection_count = connections.size();
 }
 
+void MultiplexedConnections::sendScalarsData(Scalars & data)
+{
+    std::lock_guard lock(cancel_mutex);
+
+    if (!sent_query)
+        throw Exception("Cannot send scalars data: query not yet sent.", ErrorCodes::LOGICAL_ERROR);
+
+    for (ReplicaState & state : replica_states)
+    {
+        Connection * connection = state.connection;
+        if (connection != nullptr)
+            connection->sendScalarsData(data);
+    }
+}
+
 void MultiplexedConnections::sendExternalTablesData(std::vector<ExternalTablesData> & data)
 {
     std::lock_guard lock(cancel_mutex);

dbms/src/Client/MultiplexedConnections.h

@@ -27,6 +27,8 @@ public:
         std::vector<IConnectionPool::Entry> && connections,
         const Settings & settings_, const ThrottlerPtr & throttler_);
 
+    /// Send all scalars to replicas.
+    void sendScalarsData(Scalars & data);
     /// Send all content of external tables to replicas.
     void sendExternalTablesData(std::vector<ExternalTablesData> & data);
 

dbms/src/Common/CurrentMetrics.cpp

@@ -21,6 +21,7 @@
     M(OpenFileForWrite, "Number of files open for writing") \
     M(Read, "Number of read (read, pread, io_getevents, etc.) syscalls in fly") \
     M(Write, "Number of write (write, pwrite, io_getevents, etc.) syscalls in fly") \
+    M(SendScalars, "Number of connections that are sending data for scalars to remote servers.") \
     M(SendExternalTables, "Number of connections that are sending data for external tables to remote servers. External tables are used to implement GLOBAL IN and GLOBAL JOIN operators with distributed subqueries.") \
     M(QueryThread, "Number of query processing threads") \
     M(ReadonlyReplica, "Number of Replicated tables that are currently in readonly state due to re-initialization after ZooKeeper session loss or due to startup without ZooKeeper configured.") \

dbms/src/Common/DiskSpaceMonitor.cpp

@@ -292,7 +292,7 @@ Volume::Volume(
                                     formatReadableSizeWithBinarySuffix(max_data_part_size) << ")");
     }
     constexpr UInt64 MIN_PART_SIZE = 8u * 1024u * 1024u;
-    if (max_data_part_size < MIN_PART_SIZE)
+    if (max_data_part_size != 0 && max_data_part_size < MIN_PART_SIZE)
         LOG_WARNING(logger, "Volume " << backQuote(name) << " max_data_part_size is too low ("
             << formatReadableSizeWithBinarySuffix(max_data_part_size) << " < "
             << formatReadableSizeWithBinarySuffix(MIN_PART_SIZE) << ")");

dbms/src/Common/ErrorCodes.cpp

@@ -155,7 +155,7 @@ namespace ErrorCodes
     extern const int NOT_FOUND_FUNCTION_ELEMENT_FOR_AGGREGATE = 147;
     extern const int NOT_FOUND_RELATION_ELEMENT_FOR_CONDITION = 148;
     extern const int NOT_FOUND_RHS_ELEMENT_FOR_CONDITION = 149;
-    extern const int NO_ATTRIBUTES_LISTED = 150;
+    extern const int EMPTY_LIST_OF_ATTRIBUTES_PASSED = 150;
     extern const int INDEX_OF_COLUMN_IN_SORT_CLAUSE_IS_OUT_OF_RANGE = 151;
     extern const int UNKNOWN_DIRECTION_OF_SORTING = 152;
     extern const int ILLEGAL_DIVISION = 153;
@@ -361,7 +361,7 @@ namespace ErrorCodes
     extern const int PART_IS_TEMPORARILY_LOCKED = 384;
     extern const int MULTIPLE_STREAMS_REQUIRED = 385;
     extern const int NO_COMMON_TYPE = 386;
-    extern const int EXTERNAL_LOADABLE_ALREADY_EXISTS = 387;
+    extern const int DICTIONARY_ALREADY_EXISTS = 387;
     extern const int CANNOT_ASSIGN_OPTIMIZE = 388;
     extern const int INSERT_WAS_DEDUPLICATED = 389;
     extern const int CANNOT_GET_CREATE_TABLE_QUERY = 390;
@@ -466,7 +466,6 @@ namespace ErrorCodes
     extern const int INCORRECT_DICTIONARY_DEFINITION = 489;
     extern const int UNACCEPTABLE_URL = 490;
 
-
     extern const int KEEPER_EXCEPTION = 999;
     extern const int POCO_EXCEPTION = 1000;
     extern const int STD_EXCEPTION = 1001;

dbms/src/Common/HashTable/HashTable.h

@@ -358,6 +358,12 @@ protected:
     template <typename, typename, typename, typename, typename, typename, size_t>
     friend class TwoLevelHashTable;
 
+    template <typename, typename, size_t>
+    friend class TwoLevelStringHashTable;
+
+    template <typename SubMaps>
+    friend class StringHashTable;
+
     using HashValue = size_t;
     using Self = HashTable;
     using cell_type = Cell;

dbms/src/Common/HashTable/StringHashMap.h

@@ -0,0 +1,180 @@
+#pragma once
+
+#include <Common/HashTable/HashMap.h>
+#include <Common/HashTable/HashTableAllocator.h>
+#include <Common/HashTable/StringHashTable.h>
+
+template <typename Key, typename TMapped>
+struct StringHashMapCell : public HashMapCell<Key, TMapped, StringHashTableHash, HashTableNoState>
+{
+    using Base = HashMapCell<Key, TMapped, StringHashTableHash, HashTableNoState>;
+    using Base::Base;
+    static constexpr bool need_zero_value_storage = false;
+};
+
+template<typename Key, typename Mapped>
+auto lookupResultGetMapped(StringHashMapCell<Key, Mapped> * cell) { return &cell->getSecond(); }
+
+template <typename TMapped>
+struct StringHashMapCell<StringKey16, TMapped> : public HashMapCell<StringKey16, TMapped, StringHashTableHash, HashTableNoState>
+{
+    using Base = HashMapCell<StringKey16, TMapped, StringHashTableHash, HashTableNoState>;
+    using Base::Base;
+    static constexpr bool need_zero_value_storage = false;
+    bool isZero(const HashTableNoState & state) const { return isZero(this->value.first, state); }
+    // Assuming String does not contain zero bytes. NOTE: Cannot be used in serialized method
+    static bool isZero(const StringKey16 & key, const HashTableNoState & /*state*/) { return key.low == 0; }
+    void setZero() { this->value.first.low = 0; }
+};
+
+template <typename TMapped>
+struct StringHashMapCell<StringKey24, TMapped> : public HashMapCell<StringKey24, TMapped, StringHashTableHash, HashTableNoState>
+{
+    using Base = HashMapCell<StringKey24, TMapped, StringHashTableHash, HashTableNoState>;
+    using Base::Base;
+    static constexpr bool need_zero_value_storage = false;
+    bool isZero(const HashTableNoState & state) const { return isZero(this->value.first, state); }
+    // Assuming String does not contain zero bytes. NOTE: Cannot be used in serialized method
+    static bool isZero(const StringKey24 & key, const HashTableNoState & /*state*/) { return key.a == 0; }
+    void setZero() { this->value.first.a = 0; }
+};
+
+template <typename TMapped>
+struct StringHashMapCell<StringRef, TMapped> : public HashMapCellWithSavedHash<StringRef, TMapped, StringHashTableHash, HashTableNoState>
+{
+    using Base = HashMapCellWithSavedHash<StringRef, TMapped, StringHashTableHash, HashTableNoState>;
+    using Base::Base;
+    static constexpr bool need_zero_value_storage = false;
+};
+
+template <typename TMapped, typename Allocator>
+struct StringHashMapSubMaps
+{
+    using T0 = StringHashTableEmpty<StringHashMapCell<StringRef, TMapped>>;
+    using T1 = HashMapTable<StringKey8, StringHashMapCell<StringKey8, TMapped>, StringHashTableHash, StringHashTableGrower<>, Allocator>;
+    using T2 = HashMapTable<StringKey16, StringHashMapCell<StringKey16, TMapped>, StringHashTableHash, StringHashTableGrower<>, Allocator>;
+    using T3 = HashMapTable<StringKey24, StringHashMapCell<StringKey24, TMapped>, StringHashTableHash, StringHashTableGrower<>, Allocator>;
+    using Ts = HashMapTable<StringRef, StringHashMapCell<StringRef, TMapped>, StringHashTableHash, StringHashTableGrower<>, Allocator>;
+};
+
+template <typename TMapped, typename Allocator = HashTableAllocator>
+class StringHashMap : public StringHashTable<StringHashMapSubMaps<TMapped, Allocator>>
+{
+public:
+    using Base = StringHashTable<StringHashMapSubMaps<TMapped, Allocator>>;
+    using Self = StringHashMap;
+    using Key = StringRef;
+    using key_type = StringRef;
+    using mapped_type = TMapped;
+    using value_type = typename Base::Ts::value_type;
+    using LookupResult = mapped_type *;
+
+    using Base::Base;
+
+    /// Merge every cell's value of current map into the destination map.
+    ///  Func should have signature void(Mapped & dst, Mapped & src, bool emplaced).
+    ///  Each filled cell in current map will invoke func once. If that map doesn't
+    ///  have a key equals to the given cell, a new cell gets emplaced into that map,
+    ///  and func is invoked with the third argument emplaced set to true. Otherwise
+    ///  emplaced is set to false.
+    template <typename Func>
+    void ALWAYS_INLINE mergeToViaEmplace(Self & that, Func && func)
+    {
+        if (this->m0.hasZero())
+        {
+            const bool emplace_new_zero = !that.m0.hasZero();
+            if (emplace_new_zero)
+            {
+                that.m0.setHasZero();
+            }
+
+            func(that.m0.zeroValue()->getSecond(), this->m0.zeroValue()->getSecond(),
+                 emplace_new_zero);
+        }
+
+        this->m1.mergeToViaEmplace(that.m1, func);
+        this->m2.mergeToViaEmplace(that.m2, func);
+        this->m3.mergeToViaEmplace(that.m3, func);
+        this->ms.mergeToViaEmplace(that.ms, func);
+    }
+
+    /// Merge every cell's value of current map into the destination map via find.
+    ///  Func should have signature void(Mapped & dst, Mapped & src, bool exist).
+    ///  Each filled cell in current map will invoke func once. If that map doesn't
+    ///  have a key equals to the given cell, func is invoked with the third argument
+    ///  exist set to false. Otherwise exist is set to true.
+    template <typename Func>
+    void ALWAYS_INLINE mergeToViaFind(Self & that, Func && func)
+    {
+        if (this->m0.hasZero())
+        {
+            if (that.m0.hasZero())
+            {
+                func(that.m0.zeroValue()->getSecond(), this->m0.zeroValue()->getSecond(), true);
+            }
+            else
+            {
+                func(this->m0.zeroValue()->getSecond(), this->m0.zeroValue()->getSecond(), false);
+            }
+        }
+
+        this->m1.mergeToViaFind(that.m1, func);
+        this->m2.mergeToViaFind(that.m2, func);
+        this->m3.mergeToViaFind(that.m3, func);
+        this->ms.mergeToViaFind(that.ms, func);
+    }
+
+    mapped_type & ALWAYS_INLINE operator[](Key x)
+    {
+        bool inserted;
+        LookupResult it = nullptr;
+        emplace(x, it, inserted);
+        if (inserted)
+            new (it) mapped_type();
+        return *it;
+    }
+
+    template <typename Func>
+    void ALWAYS_INLINE forEachValue(Func && func)
+    {
+        if (this->m0.size())
+        {
+            func(StringRef{}, this->m0.zeroValue()->getSecond());
+        }
+
+        for (auto & v : this->m1)
+        {
+            func(toStringRef(v.getFirst()), v.getSecond());
+        }
+
+        for (auto & v : this->m2)
+        {
+            func(toStringRef(v.getFirst()), v.getSecond());
+        }
+
+        for (auto & v : this->m3)
+        {
+            func(toStringRef(v.getFirst()), v.getSecond());
+        }
+
+        for (auto & v : this->ms)
+        {
+            func(v.getFirst(), v.getSecond());
+        }
+    }
+
+    template <typename Func>
+    void ALWAYS_INLINE forEachMapped(Func && func)
+    {
+        if (this->m0.size())
+            func(this->m0.zeroValue()->getSecond());
+        for (auto & v : this->m1)
+            func(v.getSecond());
+        for (auto & v : this->m2)
+            func(v.getSecond());
+        for (auto & v : this->m3)
+            func(v.getSecond());
+        for (auto & v : this->ms)
+            func(v.getSecond());
+    }
+};

dbms/src/Common/HashTable/StringHashTable.h

@@ -0,0 +1,371 @@
+#pragma once
+
+#include <Common/HashTable/HashMap.h>
+#include <Common/HashTable/HashTable.h>
+
+struct StringKey0
+{
+};
+
+using StringKey8 = UInt64;
+using StringKey16 = DB::UInt128;
+struct StringKey24
+{
+    UInt64 a;
+    UInt64 b;
+    UInt64 c;
+
+    bool operator==(const StringKey24 rhs) const { return a == rhs.a && b == rhs.b && c == rhs.c; }
+};
+
+inline StringRef ALWAYS_INLINE toStringRef(const StringKey8 & n)
+{
+    return {reinterpret_cast<const char *>(&n), 8ul - (__builtin_clzll(n) >> 3)};
+}
+inline StringRef ALWAYS_INLINE toStringRef(const StringKey16 & n)
+{
+    return {reinterpret_cast<const char *>(&n), 16ul - (__builtin_clzll(n.high) >> 3)};
+}
+inline StringRef ALWAYS_INLINE toStringRef(const StringKey24 & n)
+{
+    return {reinterpret_cast<const char *>(&n), 24ul - (__builtin_clzll(n.c) >> 3)};
+}
+
+struct StringHashTableHash
+{
+#if defined(__SSE4_2__)
+    size_t ALWAYS_INLINE operator()(StringKey8 key) const
+    {
+        size_t res = -1ULL;
+        res = _mm_crc32_u64(res, key);
+        return res;
+    }
+    size_t ALWAYS_INLINE operator()(StringKey16 key) const
+    {
+        size_t res = -1ULL;
+        res = _mm_crc32_u64(res, key.low);
+        res = _mm_crc32_u64(res, key.high);
+        return res;
+    }
+    size_t ALWAYS_INLINE operator()(StringKey24 key) const
+    {
+        size_t res = -1ULL;
+        res = _mm_crc32_u64(res, key.a);
+        res = _mm_crc32_u64(res, key.b);
+        res = _mm_crc32_u64(res, key.c);
+        return res;
+    }
+#else
+    size_t ALWAYS_INLINE operator()(StringKey8 key) const
+    {
+        return CityHash_v1_0_2::CityHash64(reinterpret_cast<const char *>(&key), 8);
+    }
+    size_t ALWAYS_INLINE operator()(StringKey16 key) const
+    {
+        return CityHash_v1_0_2::CityHash64(reinterpret_cast<const char *>(&key), 16);
+    }
+    size_t ALWAYS_INLINE operator()(StringKey24 key) const
+    {
+        return CityHash_v1_0_2::CityHash64(reinterpret_cast<const char *>(&key), 24);
+    }
+#endif
+    size_t ALWAYS_INLINE operator()(StringRef key) const
+    {
+        return StringRefHash()(key);
+    }
+};
+
+template <typename Cell>
+struct StringHashTableEmpty
+{
+    using Self = StringHashTableEmpty;
+
+    bool has_zero = false;
+    std::aligned_storage_t<sizeof(Cell), alignof(Cell)> zero_value_storage; /// Storage of element with zero key.
+
+public:
+    bool hasZero() const { return has_zero; }
+
+    void setHasZero()
+    {
+        has_zero = true;
+        new (zeroValue()) Cell();
+    }
+
+    void setHasZero(const Cell & other)
+    {
+        has_zero = true;
+        new (zeroValue()) Cell(other);
+    }
+
+    void clearHasZero()
+    {
+        has_zero = false;
+        if (!std::is_trivially_destructible_v<Cell>)
+            zeroValue()->~Cell();
+    }
+
+    Cell * zeroValue() { return reinterpret_cast<Cell *>(&zero_value_storage); }
+    const Cell * zeroValue() const { return reinterpret_cast<const Cell *>(&zero_value_storage); }
+
+    using LookupResult = Cell *;
+    using ConstLookupResult = const Cell *;
+
+    template <typename KeyHolder>
+    void ALWAYS_INLINE emplace(KeyHolder &&, LookupResult & it, bool & inserted, size_t /* hash */)
+    {
+        if (!hasZero())
+        {
+            setHasZero();
+            inserted = true;
+        }
+        else
+            inserted = false;
+        it = zeroValue();
+    }
+
+    template <typename Key>
+    LookupResult ALWAYS_INLINE find(Key, size_t /* hash */)
+    {
+        return hasZero() ? zeroValue() : nullptr;
+    }
+
+
+    void write(DB::WriteBuffer & wb) const { zeroValue()->write(wb); }
+    void writeText(DB::WriteBuffer & wb) const { zeroValue()->writeText(wb); }
+    void read(DB::ReadBuffer & rb) { zeroValue()->read(rb); }
+    void readText(DB::ReadBuffer & rb) { zeroValue()->readText(rb); }
+    size_t size() const { return hasZero() ? 1 : 0; }
+    bool empty() const { return !hasZero(); }
+    size_t getBufferSizeInBytes() const { return sizeof(Cell); }
+    size_t getCollisions() const { return 0; }
+};
+
+template <size_t initial_size_degree = 8>
+struct StringHashTableGrower : public HashTableGrower<initial_size_degree>
+{
+    // Smooth growing for string maps
+    void increaseSize() { this->size_degree += 1; }
+};
+
+template <typename SubMaps>
+class StringHashTable : private boost::noncopyable
+{
+protected:
+    static constexpr size_t NUM_MAPS = 5;
+    // Map for storing empty string
+    using T0 = typename SubMaps::T0;
+
+    // Short strings are stored as numbers
+    using T1 = typename SubMaps::T1;
+    using T2 = typename SubMaps::T2;
+    using T3 = typename SubMaps::T3;
+
+    // Long strings are stored as StringRef along with saved hash
+    using Ts = typename SubMaps::Ts;
+    using Self = StringHashTable;
+
+    template <typename, typename, size_t>
+    friend class TwoLevelStringHashTable;
+
+    T0 m0;
+    T1 m1;
+    T2 m2;
+    T3 m3;
+    Ts ms;
+
+public:
+    using Key = StringRef;
+    using key_type = Key;
+    using value_type = typename Ts::value_type;
+    using LookupResult = typename Ts::mapped_type *;
+
+    StringHashTable() {}
+
+    StringHashTable(size_t reserve_for_num_elements)
+        : m1{reserve_for_num_elements / 4}
+        , m2{reserve_for_num_elements / 4}
+        , m3{reserve_for_num_elements / 4}
+        , ms{reserve_for_num_elements / 4}
+    {
+    }
+
+    StringHashTable(StringHashTable && rhs) { *this = std::move(rhs); }
+    ~StringHashTable() {}
+
+public:
+    // Dispatch is written in a way that maximizes the performance:
+    // 1. Always memcpy 8 times bytes
+    // 2. Use switch case extension to generate fast dispatching table
+    // 3. Funcs are named callables that can be force_inlined
+    // NOTE: It relies on Little Endianness
+    template <typename KeyHolder, typename Func>
+    decltype(auto) ALWAYS_INLINE dispatch(KeyHolder && key_holder, Func && func)
+    {
+        const StringRef & x = keyHolderGetKey(key_holder);
+        const size_t sz = x.size;
+        if (sz == 0)
+        {
+            static constexpr StringKey0 key0{};
+            keyHolderDiscardKey(key_holder);
+            return func(m0, key0, 0);
+        }
+
+        const char * p = x.data;
+        // pending bits that needs to be shifted out
+        const char s = (-sz & 7) * 8;
+        union
+        {
+            StringKey8 k8;
+            StringKey16 k16;
+            StringKey24 k24;
+            UInt64 n[3];
+        };
+        StringHashTableHash hash;
+        switch ((sz - 1) >> 3)
+        {
+            case 0: // 1..8 bytes
+            {
+                // first half page
+                if ((reinterpret_cast<uintptr_t>(p) & 2048) == 0)
+                {
+                    memcpy(&n[0], p, 8);
+                    n[0] &= -1ul >> s;
+                }
+                else
+                {
+                    const char * lp = x.data + x.size - 8;
+                    memcpy(&n[0], lp, 8);
+                    n[0] >>= s;
+                }
+                keyHolderDiscardKey(key_holder);
+                return func(m1, k8, hash(k8));
+            }
+            case 1: // 9..16 bytes
+            {
+                memcpy(&n[0], p, 8);
+                const char * lp = x.data + x.size - 8;
+                memcpy(&n[1], lp, 8);
+                n[1] >>= s;
+                keyHolderDiscardKey(key_holder);
+                return func(m2, k16, hash(k16));
+            }
+            case 2: // 17..24 bytes
+            {
+                memcpy(&n[0], p, 16);
+                const char * lp = x.data + x.size - 8;
+                memcpy(&n[2], lp, 8);
+                n[2] >>= s;
+                keyHolderDiscardKey(key_holder);
+                return func(m3, k24, hash(k24));
+            }
+            default: // >= 25 bytes
+            {
+                return func(ms, std::forward<KeyHolder>(key_holder), hash(x));
+            }
+        }
+    }
+
+    struct EmplaceCallable
+    {
+        LookupResult & mapped;
+        bool & inserted;
+
+        EmplaceCallable(LookupResult & mapped_, bool & inserted_)
+            : mapped(mapped_), inserted(inserted_) {}
+
+        template <typename Map, typename KeyHolder>
+        void ALWAYS_INLINE operator()(Map & map, KeyHolder && key_holder, size_t hash)
+        {
+            typename Map::LookupResult result;
+            map.emplace(key_holder, result, inserted, hash);
+            mapped = lookupResultGetMapped(result);
+        }
+    };
+
+    template <typename KeyHolder>
+    void ALWAYS_INLINE emplace(KeyHolder && key_holder, LookupResult & it, bool & inserted)
+    {
+        this->dispatch(key_holder, EmplaceCallable(it, inserted));
+    }
+
+    struct FindCallable
+    {
+        // find() doesn't need any key memory management, so we don't work with
+        // any key holders here, only with normal keys. The key type is still
+        // different for every subtable, this is why it is a template parameter.
+        template <typename Submap, typename SubmapKey>
+        LookupResult ALWAYS_INLINE operator()(Submap & map, const SubmapKey & key, size_t hash)
+        {
+            return lookupResultGetMapped(map.find(key, hash));
+        }
+    };
+
+    LookupResult ALWAYS_INLINE find(Key x)
+    {
+        return dispatch(x, FindCallable{});
+    }
+
+    void write(DB::WriteBuffer & wb) const
+    {
+        m0.write(wb);
+        m1.write(wb);
+        m2.write(wb);
+        m3.write(wb);
+        ms.write(wb);
+    }
+
+    void writeText(DB::WriteBuffer & wb) const
+    {
+        m0.writeText(wb);
+        DB::writeChar(',', wb);
+        m1.writeText(wb);
+        DB::writeChar(',', wb);
+        m2.writeText(wb);
+        DB::writeChar(',', wb);
+        m3.writeText(wb);
+        DB::writeChar(',', wb);
+        ms.writeText(wb);
+    }
+
+    void read(DB::ReadBuffer & rb)
+    {
+        m0.read(rb);
+        m1.read(rb);
+        m2.read(rb);
+        m3.read(rb);
+        ms.read(rb);
+    }
+
+    void readText(DB::ReadBuffer & rb)
+    {
+        m0.readText(rb);
+        DB::assertChar(',', rb);
+        m1.readText(rb);
+        DB::assertChar(',', rb);
+        m2.readText(rb);
+        DB::assertChar(',', rb);
+        m3.readText(rb);
+        DB::assertChar(',', rb);
+        ms.readText(rb);
+    }
+
+    size_t size() const { return m0.size() + m1.size() + m2.size() + m3.size() + ms.size(); }
+
+    bool empty() const { return m0.empty() && m1.empty() && m2.empty() && m3.empty() && ms.empty(); }
+
+    size_t getBufferSizeInBytes() const
+    {
+        return m0.getBufferSizeInBytes() + m1.getBufferSizeInBytes() + m2.getBufferSizeInBytes() + m3.getBufferSizeInBytes()
+            + ms.getBufferSizeInBytes();
+    }
+
+    void clearAndShrink()
+    {
+        m1.clearHasZero();
+        m1.clearAndShrink();
+        m2.clearAndShrink();
+        m3.clearAndShrink();
+        ms.clearAndShrink();
+    }
+};

dbms/src/Common/HashTable/TwoLevelStringHashMap.h

@@ -0,0 +1,37 @@
+#pragma once
+
+#include <Common/HashTable/StringHashMap.h>
+#include <Common/HashTable/TwoLevelStringHashTable.h>
+
+template <typename TMapped, typename Allocator = HashTableAllocator, template <typename...> typename ImplTable = StringHashMap>
+class TwoLevelStringHashMap : public TwoLevelStringHashTable<StringHashMapSubMaps<TMapped, Allocator>, ImplTable<TMapped, Allocator>>
+{
+public:
+    using Key = StringRef;
+    using key_type = Key;
+    using Self = TwoLevelStringHashMap;
+    using Base = TwoLevelStringHashTable<StringHashMapSubMaps<TMapped, Allocator>, StringHashMap<TMapped, Allocator>>;
+    using Base::Base;
+    using typename Base::Impl;
+    using mapped_type = TMapped;
+    using value_type = typename Base::value_type;
+
+    using LookupResult = typename Base::LookupResult;
+
+    template <typename Func>
+    void ALWAYS_INLINE forEachMapped(Func && func)
+    {
+        for (auto i = 0u; i < this->NUM_BUCKETS; ++i)
+            return this->impls[i].forEachMapped(func);
+    }
+
+    mapped_type & ALWAYS_INLINE operator[](Key x)
+    {
+        bool inserted;
+        LookupResult it;
+        emplace(x, it, inserted);
+        if (inserted)
+            new (lookupResultGetMapped(it)) mapped_type();
+        return *lookupResultGetMapped(it);
+    }
+};

dbms/src/Common/HashTable/TwoLevelStringHashTable.h

@@ -0,0 +1,218 @@
+#pragma once
+
+#include <Common/HashTable/StringHashTable.h>
+
+template <typename SubMaps, typename ImplTable = StringHashTable<SubMaps>, size_t BITS_FOR_BUCKET = 8>
+class TwoLevelStringHashTable : private boost::noncopyable
+{
+protected:
+    using HashValue = size_t;
+    using Self = TwoLevelStringHashTable;
+
+public:
+    using Key = StringRef;
+    using Impl = ImplTable;
+
+    static constexpr size_t NUM_BUCKETS = 1ULL << BITS_FOR_BUCKET;
+    static constexpr size_t MAX_BUCKET = NUM_BUCKETS - 1;
+
+    // TODO: currently hashing contains redundant computations when doing distributed or external aggregations
+    size_t hash(const Key & x) const
+    {
+        return const_cast<Self &>(*this).dispatch(x,
+            [&](const auto &, const auto &, size_t hash) { return hash; });
+    }
+
+    size_t operator()(const Key & x) const { return hash(x); }
+
+    /// NOTE Bad for hash tables with more than 2^32 cells.
+    static size_t getBucketFromHash(size_t hash_value) { return (hash_value >> (32 - BITS_FOR_BUCKET)) & MAX_BUCKET; }
+
+public:
+    using key_type = typename Impl::key_type;
+    using value_type = typename Impl::value_type;
+    using LookupResult = typename Impl::LookupResult;
+
+    Impl impls[NUM_BUCKETS];
+
+    TwoLevelStringHashTable() {}
+
+    template <typename Source>
+    TwoLevelStringHashTable(const Source & src)
+    {
+        if (src.m0.hasZero())
+            impls[0].m0.setHasZero(*src.m0.zeroValue());
+
+        for (auto & v : src.m1)
+        {
+            size_t hash_value = v.getHash(src.m1);
+            size_t buck = getBucketFromHash(hash_value);
+            impls[buck].m1.insertUniqueNonZero(&v, hash_value);
+        }
+        for (auto & v : src.m2)
+        {
+            size_t hash_value = v.getHash(src.m2);
+            size_t buck = getBucketFromHash(hash_value);
+            impls[buck].m2.insertUniqueNonZero(&v, hash_value);
+        }
+        for (auto & v : src.m3)
+        {
+            size_t hash_value = v.getHash(src.m3);
+            size_t buck = getBucketFromHash(hash_value);
+            impls[buck].m3.insertUniqueNonZero(&v, hash_value);
+        }
+        for (auto & v : src.ms)
+        {
+            size_t hash_value = v.getHash(src.ms);
+            size_t buck = getBucketFromHash(hash_value);
+            impls[buck].ms.insertUniqueNonZero(&v, hash_value);
+        }
+    }
+
+    // This function is mostly the same as StringHashTable::dispatch, but with
+    // added bucket computation. See the comments there.
+    template <typename Func, typename KeyHolder>
+    decltype(auto) ALWAYS_INLINE dispatch(KeyHolder && key_holder, Func && func)
+    {
+        const StringRef & x = keyHolderGetKey(key_holder);
+        const size_t sz = x.size;
+        if (sz == 0)
+        {
+            static constexpr StringKey0 key0{};
+            keyHolderDiscardKey(key_holder);
+            return func(impls[0].m0, key0, 0);
+        }
+
+        const char * p = x.data;
+        // pending bits that needs to be shifted out
+        const char s = (-sz & 7) * 8;
+        union
+        {
+            StringKey8 k8;
+            StringKey16 k16;
+            StringKey24 k24;
+            UInt64 n[3];
+        };
+        StringHashTableHash hash;
+        switch ((sz - 1) >> 3)
+        {
+            case 0:
+            {
+                // first half page
+                if ((reinterpret_cast<uintptr_t>(p) & 2048) == 0)
+                {
+                    memcpy(&n[0], p, 8);
+                    n[0] &= -1ul >> s;
+                }
+                else
+                {
+                    const char * lp = x.data + x.size - 8;
+                    memcpy(&n[0], lp, 8);
+                    n[0] >>= s;
+                }
+                auto res = hash(k8);
+                auto buck = getBucketFromHash(res);
+                keyHolderDiscardKey(key_holder);
+                return func(impls[buck].m1, k8, res);
+            }
+            case 1:
+            {
+                memcpy(&n[0], p, 8);
+                const char * lp = x.data + x.size - 8;
+                memcpy(&n[1], lp, 8);
+                n[1] >>= s;
+                auto res = hash(k16);
+                auto buck = getBucketFromHash(res);
+                keyHolderDiscardKey(key_holder);
+                return func(impls[buck].m2, k16, res);
+            }
+            case 2:
+            {
+                memcpy(&n[0], p, 16);
+                const char * lp = x.data + x.size - 8;
+                memcpy(&n[2], lp, 8);
+                n[2] >>= s;
+                auto res = hash(k24);
+                auto buck = getBucketFromHash(res);
+                keyHolderDiscardKey(key_holder);
+                return func(impls[buck].m3, k24, res);
+            }
+            default:
+            {
+                auto res = hash(x);
+                auto buck = getBucketFromHash(res);
+                return func(impls[buck].ms, std::forward<KeyHolder>(key_holder), res);
+            }
+        }
+    }
+
+    template <typename KeyHolder>
+    void ALWAYS_INLINE emplace(KeyHolder && key_holder, LookupResult & it, bool & inserted)
+    {
+        dispatch(key_holder, typename Impl::EmplaceCallable{it, inserted});
+    }
+
+    LookupResult ALWAYS_INLINE find(Key x)
+    {
+        return dispatch(x, typename Impl::FindCallable{});
+    }
+
+    void write(DB::WriteBuffer & wb) const
+    {
+        for (size_t i = 0; i < NUM_BUCKETS; ++i)
+            impls[i].write(wb);
+    }
+
+    void writeText(DB::WriteBuffer & wb) const
+    {
+        for (size_t i = 0; i < NUM_BUCKETS; ++i)
+        {
+            if (i != 0)
+                DB::writeChar(',', wb);
+            impls[i].writeText(wb);
+        }
+    }
+
+    void read(DB::ReadBuffer & rb)
+    {
+        for (size_t i = 0; i < NUM_BUCKETS; ++i)
+            impls[i].read(rb);
+    }
+
+    void readText(DB::ReadBuffer & rb)
+    {
+        for (size_t i = 0; i < NUM_BUCKETS; ++i)
+        {
+            if (i != 0)
+                DB::assertChar(',', rb);
+            impls[i].readText(rb);
+        }
+    }
+
+    size_t size() const
+    {
+        size_t res = 0;
+        for (size_t i = 0; i < NUM_BUCKETS; ++i)
+            res += impls[i].size();
+
+        return res;
+    }
+
+    bool empty() const
+    {
+        for (size_t i = 0; i < NUM_BUCKETS; ++i)
+            if (!impls[i].empty())
+                return false;
+
+        return true;
+    }
+
+    size_t getBufferSizeInBytes() const
+    {
+        size_t res = 0;
+        for (size_t i = 0; i < NUM_BUCKETS; ++i)
+            res += impls[i].getBufferSizeInBytes();
+
+        return res;
+    }
+};

dbms/src/Common/XDBCBridgeHelper.h

@@ -68,7 +68,7 @@ protected:
 public:
     using Configuration = Poco::Util::AbstractConfiguration;
 
-    Context & context;
+    const Context & context;
     const Configuration & config;
 
     static constexpr inline auto DEFAULT_HOST = "localhost";
@@ -79,7 +79,7 @@ public:
     static constexpr inline auto IDENTIFIER_QUOTE_HANDLER = "/identifier_quote";
     static constexpr inline auto PING_OK_ANSWER = "Ok.";
 
-    XDBCBridgeHelper(Context & global_context_, const Poco::Timespan & http_timeout_, const std::string & connection_string_)
+    XDBCBridgeHelper(const Context & global_context_, const Poco::Timespan & http_timeout_, const std::string & connection_string_)
         : http_timeout(http_timeout_), connection_string(connection_string_), context(global_context_), config(context.getConfigRef())
     {
         size_t bridge_port = config.getUInt(BridgeHelperMixin::configPrefix() + ".port", DEFAULT_PORT);

dbms/src/Core/Protocol.h

@@ -112,7 +112,8 @@ namespace Protocol
             Cancel = 3,              /// Cancel the query execution.
             Ping = 4,                /// Check that connection to the server is alive.
             TablesStatusRequest = 5, /// Check status of tables on the server.
-            KeepAlive = 6            /// Keep the connection alive
+            KeepAlive = 6,           /// Keep the connection alive
+            Scalar = 7               /// A block of data (compressed or not).
         };
 
         inline const char * toString(UInt64 packet)

dbms/src/Core/Settings.h

@@ -379,6 +379,8 @@ struct Settings : public SettingsCollection<Settings>
     M(SettingUInt64, max_live_view_insert_blocks_before_refresh, 64, "Limit maximum number of inserted blocks after which mergeable blocks are dropped and query is re-executed.") \
     M(SettingUInt64, min_free_disk_space_for_temporary_data, 0, "The minimum disk space to keep while writing temporary data used in external sorting and aggregation.") \
     \
+    M(SettingBool, enable_scalar_subquery_optimization, true, "If it is set to true, prevent scalar subqueries from (de)serializing large scalar values and possibly avoid running the same subquery more than once.") \
+    \
     /** Obsolete settings that do nothing but left for compatibility reasons. Remove each one after half a year of obsolescence. */ \
     \
     M(SettingBool, allow_experimental_low_cardinality_type, true, "Obsolete setting, does nothing. Will be removed after 2019-08-13") \

dbms/src/Core/iostream_debug_helpers.h

@@ -6,11 +6,18 @@
 
 namespace DB
 {
+
+// Used to disable implicit casting for certain overloaded types such as Field, which leads to
+// overload resolution ambiguity.
+template <typename T> struct Dumpable;
+template <typename T>
+std::ostream & operator<<(std::ostream & stream, const typename Dumpable<T>::Type & what);
+
 class IBlockInputStream;
 std::ostream & operator<<(std::ostream & stream, const IBlockInputStream & what);
 
 class Field;
-std::ostream & operator<<(std::ostream & stream, const Field & what);
+template <> struct Dumpable<Field> { using Type = Field; };
 
 struct NameAndTypePair;
 std::ostream & operator<<(std::ostream & stream, const NameAndTypePair & what);

dbms/src/DataStreams/RemoteBlockInputStream.cpp

@@ -23,8 +23,8 @@ namespace ErrorCodes
 RemoteBlockInputStream::RemoteBlockInputStream(
         Connection & connection,
         const String & query_, const Block & header_, const Context & context_, const Settings * settings,
-        const ThrottlerPtr & throttler, const Tables & external_tables_, QueryProcessingStage::Enum stage_)
-    : header(header_), query(query_), context(context_), external_tables(external_tables_), stage(stage_)
+        const ThrottlerPtr & throttler, const Scalars & scalars_, const Tables & external_tables_, QueryProcessingStage::Enum stage_)
+    : header(header_), query(query_), context(context_), scalars(scalars_), external_tables(external_tables_), stage(stage_)
 {
     if (settings)
         context.setSettings(*settings);
@@ -38,8 +38,8 @@ RemoteBlockInputStream::RemoteBlockInputStream(
 RemoteBlockInputStream::RemoteBlockInputStream(
         std::vector<IConnectionPool::Entry> && connections,
         const String & query_, const Block & header_, const Context & context_, const Settings * settings,
-        const ThrottlerPtr & throttler, const Tables & external_tables_, QueryProcessingStage::Enum stage_)
-    : header(header_), query(query_), context(context_), external_tables(external_tables_), stage(stage_)
+        const ThrottlerPtr & throttler, const Scalars & scalars_, const Tables & external_tables_, QueryProcessingStage::Enum stage_)
+    : header(header_), query(query_), context(context_), scalars(scalars_), external_tables(external_tables_), stage(stage_)
 {
     if (settings)
         context.setSettings(*settings);
@@ -54,8 +54,8 @@ RemoteBlockInputStream::RemoteBlockInputStream(
 RemoteBlockInputStream::RemoteBlockInputStream(
         const ConnectionPoolWithFailoverPtr & pool,
         const String & query_, const Block & header_, const Context & context_, const Settings * settings,
-        const ThrottlerPtr & throttler, const Tables & external_tables_, QueryProcessingStage::Enum stage_)
-    : header(header_), query(query_), context(context_), external_tables(external_tables_), stage(stage_)
+        const ThrottlerPtr & throttler, const Scalars & scalars_, const Tables & external_tables_, QueryProcessingStage::Enum stage_)
+    : header(header_), query(query_), context(context_), scalars(scalars_), external_tables(external_tables_), stage(stage_)
 {
     if (settings)
         context.setSettings(*settings);
@@ -120,6 +120,11 @@ void RemoteBlockInputStream::cancel(bool kill)
     tryCancel("Cancelling query");
 }
 
+void RemoteBlockInputStream::sendScalars()
+{
+    multiplexed_connections->sendScalarsData(scalars);
+}
+
 void RemoteBlockInputStream::sendExternalTables()
 {
     size_t count = multiplexed_connections->size();
@@ -308,6 +313,8 @@ void RemoteBlockInputStream::sendQuery()
     established = false;
     sent_query = true;
 
+    if (settings.enable_scalar_subquery_optimization)
+        sendScalars();
     sendExternalTables();
 }
 

dbms/src/DataStreams/RemoteBlockInputStream.h

@@ -25,7 +25,7 @@ public:
     RemoteBlockInputStream(
             Connection & connection,
             const String & query_, const Block & header_, const Context & context_, const Settings * settings = nullptr,
-            const ThrottlerPtr & throttler = nullptr, const Tables & external_tables_ = Tables(),
+            const ThrottlerPtr & throttler = nullptr, const Scalars & scalars_ = Scalars(), const Tables & external_tables_ = Tables(),
             QueryProcessingStage::Enum stage_ = QueryProcessingStage::Complete);
 
     /// Accepts several connections already taken from pool.
@@ -33,7 +33,7 @@ public:
     RemoteBlockInputStream(
             std::vector<IConnectionPool::Entry> && connections,
             const String & query_, const Block & header_, const Context & context_, const Settings * settings = nullptr,
-            const ThrottlerPtr & throttler = nullptr, const Tables & external_tables_ = Tables(),
+            const ThrottlerPtr & throttler = nullptr, const Scalars & scalars_ = Scalars(), const Tables & external_tables_ = Tables(),
             QueryProcessingStage::Enum stage_ = QueryProcessingStage::Complete);
 
     /// Takes a pool and gets one or several connections from it.
@@ -41,7 +41,7 @@ public:
     RemoteBlockInputStream(
             const ConnectionPoolWithFailoverPtr & pool,
             const String & query_, const Block & header_, const Context & context_, const Settings * settings = nullptr,
-            const ThrottlerPtr & throttler = nullptr, const Tables & external_tables_ = Tables(),
+            const ThrottlerPtr & throttler = nullptr, const Scalars & scalars_ = Scalars(), const Tables & external_tables_ = Tables(),
             QueryProcessingStage::Enum stage_ = QueryProcessingStage::Complete);
 
     ~RemoteBlockInputStream() override;
@@ -71,6 +71,9 @@ public:
     Block getHeader() const override { return header; }
 
 protected:
+    /// Send all scalars to remote servers
+    void sendScalars();
+
     /// Send all temporary tables to remote servers
     void sendExternalTables();
 
@@ -103,6 +106,8 @@ private:
     String query_id = "";
     Context context;
 
+    /// Scalars needed to be sent to remote servers
+    Scalars scalars;
     /// Temporary tables needed to be sent to remote servers
     Tables external_tables;
     QueryProcessingStage::Enum stage;

dbms/src/Databases/DatabaseDictionary.cpp

@@ -19,6 +19,7 @@ namespace ErrorCodes
     extern const int LOGICAL_ERROR;
     extern const int CANNOT_GET_CREATE_TABLE_QUERY;
     extern const int SYNTAX_ERROR;
+    extern const int UNSUPPORTED_METHOD;
 }
 
 DatabaseDictionary::DatabaseDictionary(const String & name_)
@@ -27,32 +28,36 @@ DatabaseDictionary::DatabaseDictionary(const String & name_)
 {
 }
 
-void DatabaseDictionary::loadTables(Context &, bool)
+void DatabaseDictionary::loadStoredObjects(Context &, bool)
 {
 }
 
 Tables DatabaseDictionary::listTables(const Context & context, const FilterByNameFunction & filter_by_name)
 {
     Tables tables;
-    ExternalLoader::Loadables loadables;
+    ExternalLoader::LoadResults load_results;
     if (filter_by_name)
     {
         /// If `filter_by_name` is set, we iterate through all dictionaries with such names. That's why we need to load all of them.
-        loadables = context.getExternalDictionariesLoader().loadAndGet(filter_by_name);
+        context.getExternalDictionariesLoader().load(filter_by_name, load_results);
     }
     else
     {
         /// If `filter_by_name` isn't set, we iterate through only already loaded dictionaries. We don't try to load all dictionaries in this case.
-        loadables = context.getExternalDictionariesLoader().getCurrentlyLoadedObjects();
+        load_results = context.getExternalDictionariesLoader().getCurrentLoadResults();
     }
 
-    for (const auto & loadable : loadables)
+    for (const auto & [object_name, info]: load_results)
     {
-        auto dict_ptr = std::static_pointer_cast<const IDictionaryBase>(loadable);
-        auto dict_name = dict_ptr->getName();
-        const DictionaryStructure & dictionary_structure = dict_ptr->getStructure();
-        auto columns = StorageDictionary::getNamesAndTypes(dictionary_structure);
-        tables[dict_name] = StorageDictionary::create(getDatabaseName(), dict_name, ColumnsDescription{columns}, context, true, dict_name);
+        /// Load tables only from XML dictionaries, don't touch other
+        if (info.object != nullptr && info.repository_name.empty())
+        {
+            auto dict_ptr = std::static_pointer_cast<const IDictionaryBase>(info.object);
+            auto dict_name = dict_ptr->getName();
+            const DictionaryStructure & dictionary_structure = dict_ptr->getStructure();
+            auto columns = StorageDictionary::getNamesAndTypes(dictionary_structure);
+            tables[dict_name] = StorageDictionary::create(getDatabaseName(), dict_name, ColumnsDescription{columns}, context, true, dict_name);
+        }
     }
     return tables;
 }
@@ -64,6 +69,66 @@ bool DatabaseDictionary::isTableExist(
     return context.getExternalDictionariesLoader().getCurrentStatus(table_name) != ExternalLoader::Status::NOT_EXIST;
 }
 
+
+bool DatabaseDictionary::isDictionaryExist(
+    const Context & /*context*/,
+    const String & /*table_name*/) const
+{
+    return false;
+}
+
+
+DatabaseDictionariesIteratorPtr DatabaseDictionary::getDictionariesIterator(
+    const Context & /*context*/,
+    const FilterByNameFunction & /*filter_by_dictionary_name*/)
+{
+    return std::make_unique<DatabaseDictionariesSnapshotIterator>();
+}
+
+
+void DatabaseDictionary::createDictionary(
+    const Context & /*context*/,
+    const String & /*dictionary_name*/,
+    const ASTPtr & /*query*/)
+{
+    throw Exception("Dictionary engine doesn't support dictionaries.", ErrorCodes::UNSUPPORTED_METHOD);
+}
+
+void DatabaseDictionary::removeDictionary(
+    const Context & /*context*/,
+    const String & /*table_name*/)
+{
+    throw Exception("Dictionary engine doesn't support dictionaries.", ErrorCodes::UNSUPPORTED_METHOD);
+}
+
+void DatabaseDictionary::attachDictionary(
+    const String & /*dictionary_name*/, const Context & /*context*/, bool /*reload*/)
+{
+    throw Exception("Dictionary engine doesn't support dictionaries.", ErrorCodes::UNSUPPORTED_METHOD);
+}
+
+void DatabaseDictionary::detachDictionary(
+    const String & /*dictionary_name*/, const Context & /*context*/, bool /*reload*/)
+{
+    throw Exception("Dictionary engine doesn't support dictionaries.", ErrorCodes::UNSUPPORTED_METHOD);
+}
+
+
+ASTPtr DatabaseDictionary::tryGetCreateDictionaryQuery(
+    const Context & /*context*/,
+    const String & /*table_name*/) const
+{
+    return nullptr;
+}
+
+
+ASTPtr DatabaseDictionary::getCreateDictionaryQuery(
+    const Context & /*context*/,
+    const String & /*table_name*/) const
+{
+    throw Exception("Dictionary engine doesn't support dictionaries.", ErrorCodes::UNSUPPORTED_METHOD);
+}
+
 StoragePtr DatabaseDictionary::tryGetTable(
     const Context & context,
     const String & table_name) const
@@ -79,9 +144,9 @@ StoragePtr DatabaseDictionary::tryGetTable(
     return {};
 }
 
-DatabaseIteratorPtr DatabaseDictionary::getIterator(const Context & context, const FilterByNameFunction & filter_by_name)
+DatabaseTablesIteratorPtr DatabaseDictionary::getTablesIterator(const Context & context, const FilterByNameFunction & filter_by_name)
 {
-    return std::make_unique<DatabaseSnapshotIterator>(listTables(context, filter_by_name));
+    return std::make_unique<DatabaseTablesSnapshotIterator>(listTables(context, filter_by_name));
 }
 
 bool DatabaseDictionary::empty(const Context & context) const
@@ -115,7 +180,7 @@ void DatabaseDictionary::removeTable(
     throw Exception("DatabaseDictionary: removeTable() is not supported", ErrorCodes::NOT_IMPLEMENTED);
 }
 
-time_t DatabaseDictionary::getTableMetadataModificationTime(
+time_t DatabaseDictionary::getObjectMetadataModificationTime(
     const Context &,
     const String &)
 {

dbms/src/Databases/DatabaseDictionary.h

@@ -31,7 +31,7 @@ public:
         return "Dictionary";
     }
 
-    void loadTables(
+    void loadStoredObjects(
         Context & context,
         bool has_force_restore_data_flag) override;
 
@@ -39,11 +39,15 @@ public:
         const Context & context,
         const String & table_name) const override;
 
+    bool isDictionaryExist(const Context & context, const String & table_name) const override;
+
     StoragePtr tryGetTable(
         const Context & context,
         const String & table_name) const override;
 
-    DatabaseIteratorPtr getIterator(const Context & context, const FilterByNameFunction & filter_by_table_name = {}) override;
+    DatabaseTablesIteratorPtr getTablesIterator(const Context & context, const FilterByNameFunction & filter_by_table_name = {}) override;
+
+    DatabaseDictionariesIteratorPtr getDictionariesIterator(const Context & context, const FilterByNameFunction & filter_by_dictionary_name = {}) override;
 
     bool empty(const Context & context) const override;
 
@@ -53,14 +57,20 @@ public:
         const StoragePtr & table,
         const ASTPtr & query) override;
 
+    void createDictionary(
+        const Context & context, const String & dictionary_name, const ASTPtr & query) override;
+
     void removeTable(
         const Context & context,
         const String & table_name) override;
 
+    void removeDictionary(const Context & context, const String & table_name) override;
+
     void attachTable(const String & table_name, const StoragePtr & table) override;
+
     StoragePtr detachTable(const String & table_name) override;
 
-    time_t getTableMetadataModificationTime(
+    time_t getObjectMetadataModificationTime(
         const Context & context,
         const String & table_name) override;
 
@@ -74,6 +84,15 @@ public:
 
     ASTPtr getCreateDatabaseQuery(const Context & context) const override;
 
+    ASTPtr getCreateDictionaryQuery(const Context & context, const String & table_name) const override;
+
+    ASTPtr tryGetCreateDictionaryQuery(const Context & context, const String & table_name) const override;
+
+
+    void attachDictionary(const String & dictionary_name, const Context & context, bool reload) override;
+
+    void detachDictionary(const String & dictionary_name, const Context & context, bool reload) override;
+
     void shutdown() override;
 
 private:

dbms/src/Databases/DatabaseFactory.cpp

@@ -53,11 +53,13 @@ DatabasePtr DatabaseFactory::get(
     else if (engine_name == "MySQL")
     {
         const ASTFunction * engine = engine_define->engine;
-        const auto & arguments = engine->arguments->children;
 
-        if (arguments.size() != 4)
-            throw Exception("MySQL Database require mysql_hostname, mysql_database_name, mysql_username, mysql_password arguments.",
-                            ErrorCodes::BAD_ARGUMENTS);
+        if (!engine->arguments || engine->arguments->children.size() != 4)
+            throw Exception(
+                "MySQL Database require mysql_hostname, mysql_database_name, mysql_username, mysql_password arguments.",
+                ErrorCodes::BAD_ARGUMENTS);
+
+        const auto & arguments = engine->arguments->children;
 
         const auto & mysql_host_name = arguments[0]->as<ASTLiteral>()->value.safeGet<String>();
         const auto & mysql_database_name = arguments[1]->as<ASTLiteral>()->value.safeGet<String>();
@@ -74,11 +76,11 @@ DatabasePtr DatabaseFactory::get(
     else if (engine_name == "Lazy")
     {
         const ASTFunction * engine = engine_define->engine;
-        const auto & arguments = engine->arguments->children;
 
-        if (arguments.size() != 1)
-            throw Exception("Lazy database require cache_expiration_time_seconds argument.",
-                            ErrorCodes::BAD_ARGUMENTS);
+        if (!engine->arguments || engine->arguments->children.size() != 1)
+            throw Exception("Lazy database require cache_expiration_time_seconds argument", ErrorCodes::BAD_ARGUMENTS);
+
+        const auto & arguments = engine->arguments->children;
 
         const auto cache_expiration_time_seconds = arguments[0]->as<ASTLiteral>()->value.safeGet<UInt64>();
         return std::make_shared<DatabaseLazy>(database_name, metadata_path, cache_expiration_time_seconds, context);

dbms/src/Databases/DatabaseLazy.cpp

@@ -29,8 +29,6 @@ namespace ErrorCodes
 }
 
 
-static constexpr size_t METADATA_FILE_BUFFER_SIZE = 32768;
-
 
 DatabaseLazy::DatabaseLazy(const String & name_, const String & metadata_path_, time_t expiration_time_, const Context & context)
     : name(name_)
@@ -43,11 +41,11 @@ DatabaseLazy::DatabaseLazy(const String & name_, const String & metadata_path_,
 }
 
 
-void DatabaseLazy::loadTables(
+void DatabaseLazy::loadStoredObjects(
     Context & /* context */,
     bool /* has_force_restore_data_flag */)
 {
-    DatabaseOnDisk::iterateTableFiles(*this, log, [this](const String & file_name)
+    DatabaseOnDisk::iterateMetadataFiles(*this, log, [this](const String & file_name)
     {
         const std::string table_name = file_name.substr(0, file_name.size() - 4);
         attachTable(table_name, nullptr);
@@ -70,7 +68,16 @@ void DatabaseLazy::createTable(
     std::lock_guard lock(tables_mutex);
     auto it = tables_cache.find(table_name);
     if (it != tables_cache.end())
-        it->second.metadata_modification_time = DatabaseOnDisk::getTableMetadataModificationTime(*this, table_name);
+        it->second.metadata_modification_time = DatabaseOnDisk::getObjectMetadataModificationTime(*this, table_name);
+}
+
+
+void DatabaseLazy::createDictionary(
+    const Context & /*context*/,
+    const String & /*dictionary_name*/,
+    const ASTPtr & /*query*/)
+{
+    throw Exception("Lazy engine can be used only with *Log tables.", ErrorCodes::UNSUPPORTED_METHOD);
 }
 
 
@@ -82,6 +89,51 @@ void DatabaseLazy::removeTable(
     DatabaseOnDisk::removeTable(*this, context, table_name, log);
 }
 
+void DatabaseLazy::removeDictionary(
+    const Context & /*context*/,
+    const String & /*table_name*/)
+{
+    throw Exception("Lazy engine can be used only with *Log tables.", ErrorCodes::UNSUPPORTED_METHOD);
+}
+
+ASTPtr DatabaseLazy::getCreateDictionaryQuery(
+    const Context & /*context*/,
+    const String & /*table_name*/) const
+{
+    throw Exception("Lazy engine can be used only with *Log tables.", ErrorCodes::UNSUPPORTED_METHOD);
+}
+
+ASTPtr DatabaseLazy::tryGetCreateDictionaryQuery(const Context & /*context*/, const String & /*table_name*/) const
+{
+    return nullptr;
+}
+
+bool DatabaseLazy::isDictionaryExist(const Context & /*context*/, const String & /*table_name*/) const
+{
+    return false;
+}
+
+
+DatabaseDictionariesIteratorPtr DatabaseLazy::getDictionariesIterator(
+    const Context & /*context*/,
+    const FilterByNameFunction & /*filter_by_dictionary_name*/)
+{
+    return std::make_unique<DatabaseDictionariesSnapshotIterator>();
+}
+
+void DatabaseLazy::attachDictionary(
+    const String & /*dictionary_name*/,
+    const Context & /*context*/,
+    bool /*load*/)
+{
+    throw Exception("Lazy engine can be used only with *Log tables.", ErrorCodes::UNSUPPORTED_METHOD);
+}
+
+void DatabaseLazy::detachDictionary(const String & /*dictionary_name*/, const Context & /*context*/, bool /*reload*/)
+{
+    throw Exception("Lazy engine can be used only with *Log tables.", ErrorCodes::UNSUPPORTED_METHOD);
+}
+
 void DatabaseLazy::renameTable(
     const Context & context,
     const String & table_name,
@@ -94,7 +146,7 @@ void DatabaseLazy::renameTable(
 }
 
 
-time_t DatabaseLazy::getTableMetadataModificationTime(
+time_t DatabaseLazy::getObjectMetadataModificationTime(
     const Context & /* context */,
     const String & table_name)
 {
@@ -172,7 +224,7 @@ StoragePtr DatabaseLazy::tryGetTable(
     return loadTable(context, table_name);
 }
 
-DatabaseIteratorPtr DatabaseLazy::getIterator(const Context & context, const FilterByNameFunction & filter_by_table_name)
+DatabaseTablesIteratorPtr DatabaseLazy::getTablesIterator(const Context & context, const FilterByNameFunction & filter_by_table_name)
 {
     std::lock_guard lock(tables_mutex);
     Strings filtered_tables;
@@ -198,7 +250,7 @@ void DatabaseLazy::attachTable(const String & table_name, const StoragePtr & tab
 
     auto [it, inserted] = tables_cache.emplace(std::piecewise_construct,
                               std::forward_as_tuple(table_name),
-                              std::forward_as_tuple(table, current_time, DatabaseOnDisk::getTableMetadataModificationTime(*this, table_name)));
+                              std::forward_as_tuple(table, current_time, DatabaseOnDisk::getObjectMetadataModificationTime(*this, table_name)));
     if (!inserted)
         throw Exception("Table " + backQuote(getDatabaseName()) + "." + backQuote(table_name) + " already exists.", ErrorCodes::TABLE_ALREADY_EXISTS);
 
@@ -267,9 +319,9 @@ String DatabaseLazy::getDatabaseName() const
     return name;
 }
 
-String DatabaseLazy::getTableMetadataPath(const String & table_name) const
+String DatabaseLazy::getObjectMetadataPath(const String & table_name) const
 {
-    return DatabaseOnDisk::getTableMetadataPath(*this, table_name);
+    return DatabaseOnDisk::getObjectMetadataPath(*this, table_name);
 }
 
 StoragePtr DatabaseLazy::loadTable(const Context & context, const String & table_name) const
@@ -280,31 +332,18 @@ StoragePtr DatabaseLazy::loadTable(const Context & context, const String & table
 
     const String table_metadata_path = getMetadataPath() + "/" + escapeForFileName(table_name) + ".sql";
 
-    String s;
-    {
-        char in_buf[METADATA_FILE_BUFFER_SIZE];
-        ReadBufferFromFile in(table_metadata_path, METADATA_FILE_BUFFER_SIZE, -1, in_buf);
-        readStringUntilEOF(s, in);
-    }
-
-    /** Empty files with metadata are generated after a rough restart of the server.
-      * Remove these files to slightly reduce the work of the admins on startup.
-      */
-    if (s.empty())
-    {
-        LOG_ERROR(log, "LoadTable: File " << table_metadata_path << " is empty. Removing.");
-        Poco::File(table_metadata_path).remove();
-        return nullptr;
-    }
-
     try
     {
         String table_name_;
         StoragePtr table;
         Context context_copy(context); /// some tables can change context, but not LogTables
-        std::tie(table_name_, table) = createTableFromDefinition(
-            s, name, getDataPath(), context_copy, false, "in file " + table_metadata_path);
-        if (!endsWith(table->getName(), "Log"))
+
+        auto ast = parseCreateQueryFromMetadataFile(table_metadata_path, log);
+        if (ast)
+            std::tie(table_name_, table) = createTableFromAST(
+                ast->as<const ASTCreateQuery &>(), name, getDataPath(), context_copy, false);
+
+        if (!ast || !endsWith(table->getName(), "Log"))
             throw Exception("Only *Log tables can be used with Lazy database engine.", ErrorCodes::LOGICAL_ERROR);
         {
             std::lock_guard lock(tables_mutex);

dbms/src/Databases/DatabaseLazy.h

@@ -2,11 +2,13 @@
 
 #include <Databases/DatabasesCommon.h>
 #include <Interpreters/Context.h>
+#include <Parsers/ASTCreateQuery.h>
 
 
 namespace DB
 {
 
+
 class DatabaseLazyIterator;
 
 /** Lazy engine of databases.
@@ -20,7 +22,7 @@ public:
 
     String getEngineName() const override { return "Lazy"; }
 
-    void loadTables(
+    void loadStoredObjects(
         Context & context,
         bool has_force_restore_data_flag) override;
 
@@ -30,10 +32,19 @@ public:
         const StoragePtr & table,
         const ASTPtr & query) override;
 
+    void createDictionary(
+        const Context & context,
+        const String & dictionary_name,
+        const ASTPtr & query) override;
+
     void removeTable(
         const Context & context,
         const String & table_name) override;
 
+    void removeDictionary(
+        const Context & context,
+        const String & table_name) override;
+
     void renameTable(
         const Context & context,
         const String & table_name,
@@ -49,7 +60,7 @@ public:
         const ConstraintsDescription & constraints,
         const ASTModifier & engine_modifier) override;
 
-    time_t getTableMetadataModificationTime(
+    time_t getObjectMetadataModificationTime(
         const Context & context,
         const String & table_name) override;
 
@@ -61,12 +72,20 @@ public:
         const Context & context,
         const String & table_name) const override;
 
+    ASTPtr getCreateDictionaryQuery(
+        const Context & context,
+        const String & dictionary_name) const override;
+
+    ASTPtr tryGetCreateDictionaryQuery(
+        const Context & context,
+        const String & dictionary_name) const override;
+
     ASTPtr getCreateDatabaseQuery(const Context & context) const override;
 
     String getDataPath() const override;
     String getDatabaseName() const override;
     String getMetadataPath() const override;
-    String getTableMetadataPath(const String & table_name) const override;
+    String getObjectMetadataPath(const String & table_name) const override;
 
     void drop() override;
 
@@ -74,18 +93,28 @@ public:
         const Context & context,
         const String & table_name) const override;
 
+    bool isDictionaryExist(
+        const Context & context,
+        const String & table_name) const override;
+
     StoragePtr tryGetTable(
         const Context & context,
         const String & table_name) const override;
 
     bool empty(const Context & context) const override;
 
-    DatabaseIteratorPtr getIterator(const Context & context, const FilterByNameFunction & filter_by_table_name = {}) override;
+    DatabaseTablesIteratorPtr getTablesIterator(const Context & context, const FilterByNameFunction & filter_by_table_name = {}) override;
+
+    DatabaseDictionariesIteratorPtr getDictionariesIterator(const Context & context, const FilterByNameFunction & filter_by_dictionary_name = {}) override;
 
     void attachTable(const String & table_name, const StoragePtr & table) override;
 
     StoragePtr detachTable(const String & table_name) override;
 
+    void attachDictionary(const String & dictionary_name, const Context & context, bool reload) override;
+
+    void detachDictionary(const String & dictionary_name, const Context & context, bool reload) override;
+
     void shutdown() override;
 
     ~DatabaseLazy() override;
@@ -138,10 +167,13 @@ private:
 };
 
 
-class DatabaseLazyIterator final : public IDatabaseIterator
+class DatabaseLazyIterator final : public IDatabaseTablesIterator
 {
 public:
-    DatabaseLazyIterator(DatabaseLazy & database_, const Context & context_, Strings && table_names_);
+    DatabaseLazyIterator(
+        DatabaseLazy & database_,
+        const Context & context_,
+        Strings && table_names_);
 
     void next() override;
     bool isValid() const override;
@@ -155,5 +187,4 @@ private:
     Strings::const_iterator iterator;
     mutable StoragePtr current_storage;
 };
-
 }

dbms/src/Databases/DatabaseMemory.cpp

@@ -9,6 +9,8 @@ namespace DB
 namespace ErrorCodes
 {
     extern const int CANNOT_GET_CREATE_TABLE_QUERY;
+    extern const int CANNOT_GET_CREATE_DICTIONARY_QUERY;
+    extern const int UNSUPPORTED_METHOD;
 }
 
 DatabaseMemory::DatabaseMemory(String name_)
@@ -16,7 +18,7 @@ DatabaseMemory::DatabaseMemory(String name_)
     , log(&Logger::get("DatabaseMemory(" + name + ")"))
 {}
 
-void DatabaseMemory::loadTables(
+void DatabaseMemory::loadStoredObjects(
     Context & /*context*/,
     bool /*has_force_restore_data_flag*/)
 {
@@ -32,6 +34,21 @@ void DatabaseMemory::createTable(
     attachTable(table_name, table);
 }
 
+
+void DatabaseMemory::attachDictionary(const String & /*name*/, const Context & /*context*/, bool /*reload*/)
+{
+    throw Exception("There is no ATTACH DICTIONARY query for DatabaseMemory", ErrorCodes::UNSUPPORTED_METHOD);
+}
+
+void DatabaseMemory::createDictionary(
+    const Context & /*context*/,
+    const String & /*dictionary_name*/,
+    const ASTPtr & /*query*/)
+{
+    throw Exception("There is no CREATE DICTIONARY query for DatabaseMemory", ErrorCodes::UNSUPPORTED_METHOD);
+}
+
+
 void DatabaseMemory::removeTable(
     const Context & /*context*/,
     const String & table_name)
@@ -39,9 +56,23 @@ void DatabaseMemory::removeTable(
     detachTable(table_name);
 }
 
-time_t DatabaseMemory::getTableMetadataModificationTime(
-    const Context &,
-    const String &)
+
+void DatabaseMemory::detachDictionary(const String & /*name*/, const Context & /*context*/, bool /*reload*/)
+{
+    throw Exception("There is no DETACH DICTIONARY query for DatabaseMemory", ErrorCodes::UNSUPPORTED_METHOD);
+}
+
+
+void DatabaseMemory::removeDictionary(
+    const Context & /*context*/,
+    const String & /*dictionary_name*/)
+{
+    throw Exception("There is no DROP DICTIONARY query for DatabaseMemory", ErrorCodes::UNSUPPORTED_METHOD);
+}
+
+
+time_t DatabaseMemory::getObjectMetadataModificationTime(
+    const Context &, const String &)
 {
     return static_cast<time_t>(0);
 }
@@ -53,6 +84,15 @@ ASTPtr DatabaseMemory::getCreateTableQuery(
     throw Exception("There is no CREATE TABLE query for DatabaseMemory tables", ErrorCodes::CANNOT_GET_CREATE_TABLE_QUERY);
 }
 
+
+ASTPtr DatabaseMemory::getCreateDictionaryQuery(
+    const Context &,
+    const String &) const
+{
+    throw Exception("There is no CREATE DICTIONARY query for DatabaseMemory dictionaries", ErrorCodes::CANNOT_GET_CREATE_DICTIONARY_QUERY);
+}
+
+
 ASTPtr DatabaseMemory::getCreateDatabaseQuery(
     const Context &) const
 {

dbms/src/Databases/DatabaseMemory.h

@@ -23,7 +23,7 @@ public:
 
     String getEngineName() const override { return "Memory"; }
 
-    void loadTables(
+    void loadStoredObjects(
         Context & context,
         bool has_force_restore_data_flag) override;
 
@@ -33,16 +33,35 @@ public:
         const StoragePtr & table,
         const ASTPtr & query) override;
 
+    void createDictionary(
+        const Context & context,
+        const String & dictionary_name,
+        const ASTPtr & query) override;
+
+    void attachDictionary(
+        const String & name,
+        const Context & context,
+        bool reload) override;
+
     void removeTable(
         const Context & context,
         const String & table_name) override;
 
-    time_t getTableMetadataModificationTime(
+    void removeDictionary(
         const Context & context,
-        const String & table_name) override;
+        const String & dictionary_name) override;
+
+    void detachDictionary(
+        const String & name,
+        const Context & context,
+        bool reload) override;
+
+    time_t getObjectMetadataModificationTime(const Context & context, const String & table_name) override;
 
     ASTPtr getCreateTableQuery(const Context & context, const String & table_name) const override;
+    ASTPtr getCreateDictionaryQuery(const Context & context, const String & table_name) const override;
     ASTPtr tryGetCreateTableQuery(const Context &, const String &) const override { return nullptr; }
+    ASTPtr tryGetCreateDictionaryQuery(const Context &, const String &) const override { return nullptr; }
 
     ASTPtr getCreateDatabaseQuery(const Context & context) const override;
 

dbms/src/Databases/DatabaseMySQL.cpp

@@ -64,7 +64,7 @@ bool DatabaseMySQL::empty(const Context &) const
     return local_tables_cache.empty();
 }
 
-DatabaseIteratorPtr DatabaseMySQL::getIterator(const Context &, const FilterByNameFunction & filter_by_table_name)
+DatabaseTablesIteratorPtr DatabaseMySQL::getTablesIterator(const Context &, const FilterByNameFunction & filter_by_table_name)
 {
     Tables tables;
     std::lock_guard<std::mutex> lock(mutex);
@@ -75,7 +75,7 @@ DatabaseIteratorPtr DatabaseMySQL::getIterator(const Context &, const FilterByNa
         if (!filter_by_table_name || filter_by_table_name(local_table.first))
             tables[local_table.first] = local_table.second.storage;
 
-    return std::make_unique<DatabaseSnapshotIterator>(tables);
+    return std::make_unique<DatabaseTablesSnapshotIterator>(tables);
 }
 
 bool DatabaseMySQL::isTableExist(const Context & context, const String & name) const
@@ -107,7 +107,7 @@ ASTPtr DatabaseMySQL::tryGetCreateTableQuery(const Context &, const String & tab
     return local_tables_cache[table_name].create_table_query;
 }
 
-time_t DatabaseMySQL::getTableMetadataModificationTime(const Context &, const String & table_name)
+time_t DatabaseMySQL::getObjectMetadataModificationTime(const Context &, const String & table_name)
 {
     std::lock_guard<std::mutex> lock(mutex);
 

dbms/src/Databases/DatabaseMySQL.h

@@ -6,6 +6,7 @@
 #include <mysqlxx/Pool.h>
 #include <Databases/DatabasesCommon.h>
 #include <Interpreters/Context.h>
+#include <memory>
 
 
 namespace DB
@@ -29,17 +30,32 @@ public:
 
     bool empty(const Context & context) const override;
 
-    DatabaseIteratorPtr getIterator(const Context & context, const FilterByNameFunction & filter_by_table_name = {}) override;
+    DatabaseTablesIteratorPtr getTablesIterator(const Context & context, const FilterByNameFunction & filter_by_table_name = {}) override;
+
+    DatabaseDictionariesIteratorPtr getDictionariesIterator(const Context &, const FilterByNameFunction & = {}) override
+    {
+        return std::make_unique<DatabaseDictionariesSnapshotIterator>();
+    }
 
     ASTPtr getCreateDatabaseQuery(const Context & context) const override;
 
     bool isTableExist(const Context & context, const String & name) const override;
 
+    bool isDictionaryExist(const Context &, const String &) const override { return false; }
+
     StoragePtr tryGetTable(const Context & context, const String & name) const override;
 
     ASTPtr tryGetCreateTableQuery(const Context & context, const String & name) const override;
 
-    time_t getTableMetadataModificationTime(const Context & context, const String & name) override;
+    ASTPtr getCreateDictionaryQuery(const Context &, const String &) const override
+    {
+        throw Exception("MySQL database engine does not support dictionaries.", ErrorCodes::NOT_IMPLEMENTED);
+    }
+
+    ASTPtr tryGetCreateDictionaryQuery(const Context &, const String &) const override { return nullptr; }
+
+
+    time_t getObjectMetadataModificationTime(const Context & context, const String & name) override;
 
     void shutdown() override;
 
@@ -48,7 +64,12 @@ public:
         throw Exception("MySQL database engine does not support detach table.", ErrorCodes::NOT_IMPLEMENTED);
     }
 
-    void loadTables(Context &, bool) override
+    void detachDictionary(const String &, const Context &, bool) override
+    {
+        throw Exception("MySQL database engine does not support detach dictionary.", ErrorCodes::NOT_IMPLEMENTED);
+    }
+
+    void loadStoredObjects(Context &, bool) override
     {
         /// do nothing
     }
@@ -58,16 +79,33 @@ public:
         throw Exception("MySQL database engine does not support remove table.", ErrorCodes::NOT_IMPLEMENTED);
     }
 
+    void removeDictionary(const Context &, const String &) override
+    {
+        throw Exception("MySQL database engine does not support remove dictionary.", ErrorCodes::NOT_IMPLEMENTED);
+    }
+
+
     void attachTable(const String &, const StoragePtr &) override
     {
         throw Exception("MySQL database engine does not support attach table.", ErrorCodes::NOT_IMPLEMENTED);
     }
 
+    void attachDictionary(const String &, const Context &, bool) override
+    {
+        throw Exception("MySQL database engine does not support attach dictionary.", ErrorCodes::NOT_IMPLEMENTED);
+    }
+
     void createTable(const Context &, const String &, const StoragePtr &, const ASTPtr &) override
     {
         throw Exception("MySQL database engine does not support create table.", ErrorCodes::NOT_IMPLEMENTED);
     }
 
+    void createDictionary(const Context &, const String &, const ASTPtr &) override
+    {
+        throw Exception("MySQL database engine does not support create dictionary.", ErrorCodes::NOT_IMPLEMENTED);
+    }
+
+
 private:
     struct MySQLStorageInfo
     {

dbms/src/Databases/DatabaseOnDisk.cpp

@@ -1,37 +1,49 @@
 #include <Databases/DatabaseOnDisk.h>
 
-#include <Common/escapeForFileName.h>
-#include <Interpreters/Context.h>
-#include <Interpreters/InterpreterCreateQuery.h>
 #include <IO/ReadBufferFromFile.h>
 #include <IO/ReadHelpers.h>
 #include <IO/WriteBufferFromFile.h>
 #include <IO/WriteHelpers.h>
+#include <Interpreters/Context.h>
+#include <Interpreters/InterpreterCreateQuery.h>
+#include <Interpreters/ExternalDictionariesLoader.h>
+#include <Dictionaries/getDictionaryConfigurationFromAST.h>
 #include <Parsers/ASTCreateQuery.h>
-#include <Parsers/parseQuery.h>
 #include <Parsers/ParserCreateQuery.h>
+#include <Parsers/formatAST.h>
+#include <Parsers/parseQuery.h>
 #include <Storages/IStorage.h>
+#include <Storages/StorageFactory.h>
+#include <TableFunctions/TableFunctionFactory.h>
+#include <Common/escapeForFileName.h>
 
 #include <common/logger_useful.h>
 #include <Poco/DirectoryIterator.h>
 
+
+
 namespace DB
 {
 
+static constexpr size_t METADATA_FILE_BUFFER_SIZE = 32768;
+
 namespace ErrorCodes
 {
     extern const int CANNOT_GET_CREATE_TABLE_QUERY;
+    extern const int CANNOT_GET_CREATE_DICTIONARY_QUERY;
     extern const int FILE_DOESNT_EXIST;
     extern const int INCORRECT_FILE_NAME;
     extern const int SYNTAX_ERROR;
     extern const int TABLE_ALREADY_EXISTS;
     extern const int UNKNOWN_TABLE;
+    extern const int DICTIONARY_ALREADY_EXISTS;
+    extern const int EMPTY_LIST_OF_COLUMNS_PASSED;
 }
 
 
 namespace detail
 {
-    String getTableMetadataPath(const String & base_path, const String & table_name)
+    String getObjectMetadataPath(const String & base_path, const String & table_name)
     {
         return base_path + (endsWith(base_path, "/") ? "" : "/") + escapeForFileName(table_name) + ".sql";
     }
@@ -85,6 +97,107 @@ namespace detail
     }
 }
 
+
+ASTPtr parseCreateQueryFromMetadataFile(const String & filepath, Poco::Logger * log)
+{
+    String definition;
+    {
+        char in_buf[METADATA_FILE_BUFFER_SIZE];
+        ReadBufferFromFile in(filepath, METADATA_FILE_BUFFER_SIZE, -1, in_buf);
+        readStringUntilEOF(definition, in);
+    }
+
+    /** Empty files with metadata are generated after a rough restart of the server.
+      * Remove these files to slightly reduce the work of the admins on startup.
+      */
+    if (definition.empty())
+    {
+        LOG_ERROR(log, "File " << filepath << " is empty. Removing.");
+        Poco::File(filepath).remove();
+        return nullptr;
+    }
+
+    ParserCreateQuery parser_create;
+    ASTPtr result = parseQuery(parser_create, definition, "in file " + filepath, 0);
+    return result;
+}
+
+
+
+std::pair<String, StoragePtr> createTableFromAST(
+    ASTCreateQuery ast_create_query,
+    const String & database_name,
+    const String & database_data_path,
+    Context & context,
+    bool has_force_restore_data_flag)
+{
+    ast_create_query.attach = true;
+    ast_create_query.database = database_name;
+
+    if (ast_create_query.as_table_function)
+    {
+        const auto & table_function = ast_create_query.as_table_function->as<ASTFunction &>();
+        const auto & factory = TableFunctionFactory::instance();
+        StoragePtr storage = factory.get(table_function.name, context)->execute(ast_create_query.as_table_function, context, ast_create_query.table);
+        return {ast_create_query.table, storage};
+    }
+    /// We do not directly use `InterpreterCreateQuery::execute`, because
+    /// - the database has not been created yet;
+    /// - the code is simpler, since the query is already brought to a suitable form.
+    if (!ast_create_query.columns_list || !ast_create_query.columns_list->columns)
+        throw Exception("Missing definition of columns.", ErrorCodes::EMPTY_LIST_OF_COLUMNS_PASSED);
+
+    ColumnsDescription columns = InterpreterCreateQuery::getColumnsDescription(*ast_create_query.columns_list->columns, context);
+    ConstraintsDescription constraints = InterpreterCreateQuery::getConstraintsDescription(ast_create_query.columns_list->constraints);
+
+    return
+    {
+        ast_create_query.table,
+        StorageFactory::instance().get(
+            ast_create_query,
+            database_data_path, ast_create_query.table, database_name, context, context.getGlobalContext(),
+            columns, constraints,
+            true, has_force_restore_data_flag)
+    };
+}
+
+
+String getObjectDefinitionFromCreateQuery(const ASTPtr & query)
+{
+    ASTPtr query_clone = query->clone();
+    auto * create = query_clone->as<ASTCreateQuery>();
+
+    if (!create)
+    {
+        std::ostringstream query_stream;
+        formatAST(*create, query_stream, true);
+        throw Exception("Query '" + query_stream.str() + "' is not CREATE query", ErrorCodes::LOGICAL_ERROR);
+    }
+
+    if (!create->is_dictionary)
+        create->attach = true;
+
+    /// We remove everything that is not needed for ATTACH from the query.
+    create->database.clear();
+    create->as_database.clear();
+    create->as_table.clear();
+    create->if_not_exists = false;
+    create->is_populate = false;
+    create->replace_view = false;
+
+    /// For views it is necessary to save the SELECT query itself, for the rest - on the contrary
+    if (!create->is_view && !create->is_materialized_view && !create->is_live_view)
+        create->select = nullptr;
+
+    create->format = nullptr;
+    create->out_file = nullptr;
+
+    std::ostringstream statement_stream;
+    formatAST(*create, statement_stream, false);
+    statement_stream << '\n';
+    return statement_stream.str();
+}
+
 void DatabaseOnDisk::createTable(
     IDatabase & database,
     const Context & context,
@@ -106,15 +219,19 @@ void DatabaseOnDisk::createTable(
     /// A race condition would be possible if a table with the same name is simultaneously created using CREATE and using ATTACH.
     /// But there is protection from it - see using DDLGuard in InterpreterCreateQuery.
 
+    if (database.isDictionaryExist(context, table_name))
+        throw Exception("Dictionary " + backQuote(database.getDatabaseName()) + "." + backQuote(table_name) + " already exists.",
+            ErrorCodes::DICTIONARY_ALREADY_EXISTS);
+
     if (database.isTableExist(context, table_name))
         throw Exception("Table " + backQuote(database.getDatabaseName()) + "." + backQuote(table_name) + " already exists.", ErrorCodes::TABLE_ALREADY_EXISTS);
 
-    String table_metadata_path = database.getTableMetadataPath(table_name);
+    String table_metadata_path = database.getObjectMetadataPath(table_name);
     String table_metadata_tmp_path = table_metadata_path + ".tmp";
     String statement;
 
     {
-        statement = getTableDefinitionFromCreateQuery(query);
+        statement = getObjectDefinitionFromCreateQuery(query);
 
         /// Exclusive flags guarantees, that table is not created right now in another thread. Otherwise, exception will be thrown.
         WriteBufferFromFile out(table_metadata_tmp_path, statement.size(), O_WRONLY | O_CREAT | O_EXCL);
@@ -141,6 +258,70 @@ void DatabaseOnDisk::createTable(
     }
 }
 
+
+void DatabaseOnDisk::createDictionary(
+    IDatabase & database,
+    const Context & context,
+    const String & dictionary_name,
+    const ASTPtr & query)
+{
+    const auto & settings = context.getSettingsRef();
+
+    /** The code is based on the assumption that all threads share the same order of operations
+      * - creating the .sql.tmp file;
+      * - adding a dictionary to `dictionaries`;
+      * - rename .sql.tmp to .sql.
+      */
+
+    /// A race condition would be possible if a dictionary with the same name is simultaneously created using CREATE and using ATTACH.
+    /// But there is protection from it - see using DDLGuard in InterpreterCreateQuery.
+    if (database.isDictionaryExist(context, dictionary_name))
+        throw Exception("Dictionary " + backQuote(database.getDatabaseName()) + "." + backQuote(dictionary_name) + " already exists.", ErrorCodes::DICTIONARY_ALREADY_EXISTS);
+
+    if (database.isTableExist(context, dictionary_name))
+        throw Exception("Table " + backQuote(database.getDatabaseName()) + "." + backQuote(dictionary_name) + " already exists.", ErrorCodes::TABLE_ALREADY_EXISTS);
+
+
+    String dictionary_metadata_path = database.getObjectMetadataPath(dictionary_name);
+    String dictionary_metadata_tmp_path = dictionary_metadata_path + ".tmp";
+    String statement;
+
+    {
+        statement = getObjectDefinitionFromCreateQuery(query);
+
+        /// Exclusive flags guarantees, that table is not created right now in another thread. Otherwise, exception will be thrown.
+        WriteBufferFromFile out(dictionary_metadata_tmp_path, statement.size(), O_WRONLY | O_CREAT | O_EXCL);
+        writeString(statement, out);
+        out.next();
+        if (settings.fsync_metadata)
+            out.sync();
+        out.close();
+    }
+
+    try
+    {
+        /// Do not load it now because we want more strict loading
+        database.attachDictionary(dictionary_name, context, false);
+        /// Load dictionary
+        bool lazy_load = context.getConfigRef().getBool("dictionaries_lazy_load", true);
+        String dict_name = database.getDatabaseName() + "." + dictionary_name;
+        context.getExternalDictionariesLoader().addDictionaryWithConfig(
+            dict_name, database.getDatabaseName(), query->as<const ASTCreateQuery &>(), !lazy_load);
+
+        /// If it was ATTACH query and file with dictionary metadata already exist
+        /// (so, ATTACH is done after DETACH), then rename atomically replaces old file with new one.
+        Poco::File(dictionary_metadata_tmp_path).renameTo(dictionary_metadata_path);
+
+    }
+    catch (...)
+    {
+        database.detachDictionary(dictionary_name, context);
+        Poco::File(dictionary_metadata_tmp_path).remove();
+        throw;
+    }
+}
+
+
 void DatabaseOnDisk::removeTable(
     IDatabase & database,
     const Context & /* context */,
@@ -149,7 +330,7 @@ void DatabaseOnDisk::removeTable(
 {
     StoragePtr res = database.detachTable(table_name);
 
-    String table_metadata_path = database.getTableMetadataPath(table_name);
+    String table_metadata_path = database.getObjectMetadataPath(table_name);
 
     try
     {
@@ -171,12 +352,39 @@ void DatabaseOnDisk::removeTable(
     }
 }
 
-ASTPtr DatabaseOnDisk::getCreateTableQueryImpl(const IDatabase & database, const Context & context,
-                                                 const String & table_name, bool throw_on_error)
+
+void DatabaseOnDisk::removeDictionary(
+    IDatabase & database,
+    const Context & context,
+    const String & dictionary_name,
+    Poco::Logger * /*log*/)
+{
+    database.detachDictionary(dictionary_name, context);
+
+    String dictionary_metadata_path = database.getObjectMetadataPath(dictionary_name);
+
+    try
+    {
+        Poco::File(dictionary_metadata_path).remove();
+    }
+    catch (...)
+    {
+        /// If remove was not possible for some reason
+        database.attachDictionary(dictionary_name, context);
+        throw;
+    }
+}
+
+
+ASTPtr DatabaseOnDisk::getCreateTableQueryImpl(
+    const IDatabase & database,
+    const Context & context,
+    const String & table_name,
+    bool throw_on_error)
 {
     ASTPtr ast;
 
-    auto table_metadata_path = detail::getTableMetadataPath(database.getMetadataPath(), table_name);
+    auto table_metadata_path = detail::getObjectMetadataPath(database.getMetadataPath(), table_name);
     ast = detail::getCreateQueryFromMetadata(table_metadata_path, database.getDatabaseName(), throw_on_error);
     if (!ast && throw_on_error)
     {
@@ -193,6 +401,30 @@ ASTPtr DatabaseOnDisk::getCreateTableQueryImpl(const IDatabase & database, const
     return ast;
 }
 
+
+ASTPtr DatabaseOnDisk::getCreateDictionaryQueryImpl(
+    const IDatabase & database,
+    const Context & context,
+    const String & dictionary_name,
+    bool throw_on_error)
+{
+    ASTPtr ast;
+
+    auto dictionary_metadata_path = detail::getObjectMetadataPath(database.getMetadataPath(), dictionary_name);
+    ast = detail::getCreateQueryFromMetadata(dictionary_metadata_path, database.getDatabaseName(), throw_on_error);
+    if (!ast && throw_on_error)
+    {
+        /// Handle system.* tables for which there are no table.sql files.
+        bool has_dictionary = database.isDictionaryExist(context, dictionary_name);
+
+        auto msg = has_dictionary ? "There is no CREATE DICTIONARY query for table " : "There is no metadata file for dictionary ";
+
+        throw Exception(msg + backQuote(dictionary_name), ErrorCodes::CANNOT_GET_CREATE_DICTIONARY_QUERY);
+    }
+
+    return ast;
+}
+
 ASTPtr DatabaseOnDisk::getCreateTableQuery(const IDatabase & database, const Context & context, const String & table_name)
 {
     return getCreateTableQueryImpl(database, context, table_name, true);
@@ -203,6 +435,17 @@ ASTPtr DatabaseOnDisk::tryGetCreateTableQuery(const IDatabase & database, const
     return getCreateTableQueryImpl(database, context, table_name, false);
 }
 
+
+ASTPtr DatabaseOnDisk::getCreateDictionaryQuery(const IDatabase & database, const Context & context, const String & dictionary_name)
+{
+    return getCreateDictionaryQueryImpl(database, context, dictionary_name, true);
+}
+
+ASTPtr DatabaseOnDisk::tryGetCreateDictionaryQuery(const IDatabase & database, const Context & context, const String & dictionary_name)
+{
+    return getCreateDictionaryQueryImpl(database, context, dictionary_name, false);
+}
+
 ASTPtr DatabaseOnDisk::getCreateDatabaseQuery(const IDatabase & database, const Context & /*context*/)
 {
     ASTPtr ast;
@@ -226,29 +469,25 @@ void DatabaseOnDisk::drop(const IDatabase & database)
     Poco::File(database.getMetadataPath()).remove(false);
 }
 
-String DatabaseOnDisk::getTableMetadataPath(const IDatabase & database, const String & table_name)
+String DatabaseOnDisk::getObjectMetadataPath(const IDatabase & database, const String & table_name)
 {
-    return detail::getTableMetadataPath(database.getMetadataPath(), table_name);
+    return detail::getObjectMetadataPath(database.getMetadataPath(), table_name);
 }
 
-time_t DatabaseOnDisk::getTableMetadataModificationTime(
+time_t DatabaseOnDisk::getObjectMetadataModificationTime(
     const IDatabase & database,
     const String & table_name)
 {
-    String table_metadata_path = getTableMetadataPath(database, table_name);
+    String table_metadata_path = getObjectMetadataPath(database, table_name);
     Poco::File meta_file(table_metadata_path);
 
     if (meta_file.exists())
-    {
         return meta_file.getLastModified().epochTime();
-    }
     else
-    {
         return static_cast<time_t>(0);
-    }
 }
 
-void DatabaseOnDisk::iterateTableFiles(const IDatabase & database, Poco::Logger * log, const IteratingFunction & iterating_function)
+void DatabaseOnDisk::iterateMetadataFiles(const IDatabase & database, Poco::Logger * log, const IteratingFunction & iterating_function)
 {
     Poco::DirectoryIterator dir_end;
     for (Poco::DirectoryIterator dir_it(database.getMetadataPath()); dir_it != dir_end; ++dir_it)
@@ -265,11 +504,11 @@ void DatabaseOnDisk::iterateTableFiles(const IDatabase & database, Poco::Logger
         static const char * tmp_drop_ext = ".sql.tmp_drop";
         if (endsWith(dir_it.name(), tmp_drop_ext))
         {
-            const std::string table_name = dir_it.name().substr(0, dir_it.name().size() - strlen(tmp_drop_ext));
-            if (Poco::File(database.getDataPath() + '/' + table_name).exists())
+            const std::string object_name = dir_it.name().substr(0, dir_it.name().size() - strlen(tmp_drop_ext));
+            if (Poco::File(database.getDataPath() + '/' + object_name).exists())
             {
-                Poco::File(dir_it->path()).renameTo(table_name + ".sql");
-                LOG_WARNING(log, "Table " << backQuote(table_name) << " was not dropped previously");
+                Poco::File(dir_it->path()).renameTo(object_name + ".sql");
+                LOG_WARNING(log, "Object " << backQuote(object_name) << " was not dropped previously");
             }
             else
             {

dbms/src/Databases/DatabaseOnDisk.h

@@ -13,12 +13,28 @@ namespace DB
 
 namespace detail
 {
-    String getTableMetadataPath(const String & base_path, const String & table_name);
+    String getObjectMetadataPath(const String & base_path, const String & dictionary_name);
     String getDatabaseMetadataPath(const String & base_path);
     ASTPtr getQueryFromMetadata(const String & metadata_path, bool throw_on_error = true);
     ASTPtr getCreateQueryFromMetadata(const String & metadata_path, const String & database, bool throw_on_error);
 }
 
+ASTPtr parseCreateQueryFromMetadataFile(const String & filepath, Poco::Logger * log);
+
+std::pair<String, StoragePtr> createTableFromAST(
+    ASTCreateQuery ast_create_query,
+    const String & database_name,
+    const String & database_data_path,
+    Context & context,
+    bool has_force_restore_data_flag);
+
+/** Get the row with the table definition based on the CREATE query.
+  * It is an ATTACH query that you can execute to create a table from the correspondent database.
+  * See the implementation.
+  */
+String getObjectDefinitionFromCreateQuery(const ASTPtr & query);
+
+
 /* Class to provide basic operations with tables when metadata is stored on disk in .sql files.
  */
 class DatabaseOnDisk
@@ -31,12 +47,24 @@ public:
         const StoragePtr & table,
         const ASTPtr & query);
 
+    static void createDictionary(
+        IDatabase & database,
+        const Context & context,
+        const String & dictionary_name,
+        const ASTPtr & query);
+
     static void removeTable(
         IDatabase & database,
         const Context & context,
         const String & table_name,
         Poco::Logger * log);
 
+    static void removeDictionary(
+        IDatabase & database,
+        const Context & context,
+        const String & dictionary_name,
+        Poco::Logger * log);
+
     template <typename Database>
     static void renameTable(
         IDatabase & database,
@@ -56,23 +84,33 @@ public:
         const Context & context,
         const String & table_name);
 
+    static ASTPtr getCreateDictionaryQuery(
+        const IDatabase & database,
+        const Context & context,
+        const String & dictionary_name);
+
+    static ASTPtr tryGetCreateDictionaryQuery(
+        const IDatabase & database,
+        const Context & context,
+        const String & dictionary_name);
+
     static ASTPtr getCreateDatabaseQuery(
         const IDatabase & database,
         const Context & context);
 
     static void drop(const IDatabase & database);
 
-    static String getTableMetadataPath(
+    static String getObjectMetadataPath(
         const IDatabase & database,
-        const String & table_name);
+        const String & object_name);
 
-    static time_t getTableMetadataModificationTime(
+    static time_t getObjectMetadataModificationTime(
         const IDatabase & database,
-        const String & table_name);
+        const String & object_name);
 
 
     using IteratingFunction = std::function<void(const String &)>;
-    static void iterateTableFiles(const IDatabase & database, Poco::Logger * log, const IteratingFunction & iterating_function);
+    static void iterateMetadataFiles(const IDatabase & database, Poco::Logger * log, const IteratingFunction & iterating_function);
 
 private:
     static ASTPtr getCreateTableQueryImpl(
@@ -80,6 +118,12 @@ private:
         const Context & context,
         const String & table_name,
         bool throw_on_error);
+
+    static ASTPtr getCreateDictionaryQueryImpl(
+        const IDatabase & database,
+        const Context & context,
+        const String & dictionary_name,
+        bool throw_on_error);
 };
 
 
@@ -126,7 +170,7 @@ void DatabaseOnDisk::renameTable(
         throw Exception{Exception::CreateFromPoco, e};
     }
 
-    ASTPtr ast = detail::getQueryFromMetadata(detail::getTableMetadataPath(database.getMetadataPath(), table_name));
+    ASTPtr ast = detail::getQueryFromMetadata(detail::getObjectMetadataPath(database.getMetadataPath(), table_name));
     if (!ast)
         throw Exception("There is no metadata file for table " + backQuote(table_name) + ".", ErrorCodes::FILE_DOESNT_EXIST);
     ast->as<ASTCreateQuery &>().table = to_table_name;

dbms/src/Databases/DatabaseOrdinary.cpp

@@ -11,10 +11,17 @@
 #include <IO/WriteHelpers.h>
 #include <Interpreters/Context.h>
 #include <Interpreters/InterpreterCreateQuery.h>
+#include <Interpreters/ExternalLoaderDatabaseConfigRepository.h>
+#include <Interpreters/ExternalDictionariesLoader.h>
 #include <Parsers/ASTCreateQuery.h>
 #include <Parsers/ParserCreateQuery.h>
+#include <Parsers/ParserDictionary.h>
+#include <Storages/StorageFactory.h>
+#include <Dictionaries/DictionaryFactory.h>
 #include <Parsers/parseQuery.h>
+#include <Parsers/formatAST.h>
 #include <Storages/IStorage.h>
+#include <TableFunctions/TableFunctionFactory.h>
 
 #include <Poco/DirectoryIterator.h>
 #include <Poco/Event.h>
@@ -33,59 +40,64 @@ namespace DB
 namespace ErrorCodes
 {
     extern const int CANNOT_CREATE_TABLE_FROM_METADATA;
+    extern const int CANNOT_CREATE_DICTIONARY_FROM_METADATA;
+    extern const int EMPTY_LIST_OF_COLUMNS_PASSED;
+    extern const int CANNOT_PARSE_TEXT;
+    extern const int EMPTY_LIST_OF_ATTRIBUTES_PASSED;
 }
 
 
-static constexpr size_t PRINT_MESSAGE_EACH_N_TABLES = 256;
+static constexpr size_t PRINT_MESSAGE_EACH_N_OBJECTS = 256;
 static constexpr size_t PRINT_MESSAGE_EACH_N_SECONDS = 5;
 static constexpr size_t METADATA_FILE_BUFFER_SIZE = 32768;
 
-static void loadTable(
-    Context & context,
-    const String & database_metadata_path,
-    DatabaseOrdinary & database,
-    const String & database_name,
-    const String & database_data_path,
-    const String & file_name,
-    bool has_force_restore_data_flag)
+namespace
 {
-    Logger * log = &Logger::get("loadTable");
 
-    const String table_metadata_path = database_metadata_path + "/" + file_name;
 
-    String s;
+void loadObject(
+    Context & context,
+    const ASTCreateQuery & query,
+    DatabaseOrdinary & database,
+    const String database_data_path,
+    const String & database_name,
+    bool has_force_restore_data_flag)
+try
+{
+    if (query.is_dictionary)
     {
-        char in_buf[METADATA_FILE_BUFFER_SIZE];
-        ReadBufferFromFile in(table_metadata_path, METADATA_FILE_BUFFER_SIZE, -1, in_buf);
-        readStringUntilEOF(s, in);
+        String dictionary_name = query.table;
+        database.attachDictionary(dictionary_name, context, false);
     }
-
-    /** Empty files with metadata are generated after a rough restart of the server.
-      * Remove these files to slightly reduce the work of the admins on startup.
-      */
-    if (s.empty())
-    {
-        LOG_ERROR(log, "File " << table_metadata_path << " is empty. Removing.");
-        Poco::File(table_metadata_path).remove();
-        return;
-    }
-
-    try
+    else
     {
         String table_name;
         StoragePtr table;
-        std::tie(table_name, table) = createTableFromDefinition(
-            s, database_name, database_data_path, context, has_force_restore_data_flag, "in file " + table_metadata_path);
+        std::tie(table_name, table)
+            = createTableFromAST(query, database_name, database_data_path, context, has_force_restore_data_flag);
         database.attachTable(table_name, table);
     }
-    catch (const Exception & e)
+}
+catch (const Exception & e)
+{
+    throw Exception(
+        "Cannot create object '" + query.table + "' from query " + serializeAST(query) + ", error: " + e.displayText() + ", stack trace:\n"
+            + e.getStackTrace().toString(),
+        ErrorCodes::CANNOT_CREATE_TABLE_FROM_METADATA);
+}
+
+
+void logAboutProgress(Poco::Logger * log, size_t processed, size_t total, AtomicStopwatch & watch)
+{
+    if (processed % PRINT_MESSAGE_EACH_N_OBJECTS == 0 || watch.compareAndRestart(PRINT_MESSAGE_EACH_N_SECONDS))
     {
-        throw Exception("Cannot create table from metadata file " + table_metadata_path + ", error: " + e.displayText() +
-            ", stack trace:\n" + e.getStackTrace().toString(),
-            ErrorCodes::CANNOT_CREATE_TABLE_FROM_METADATA);
+        LOG_INFO(log, std::fixed << std::setprecision(2) << processed * 100.0 / total << "%");
+        watch.restart();
     }
 }
 
+}
+
 
 DatabaseOrdinary::DatabaseOrdinary(String name_, const String & metadata_path_, const Context & context)
     : DatabaseWithOwnTablesBase(std::move(name_))
@@ -97,57 +109,78 @@ DatabaseOrdinary::DatabaseOrdinary(String name_, const String & metadata_path_,
 }
 
 
-void DatabaseOrdinary::loadTables(
+void DatabaseOrdinary::loadStoredObjects(
     Context & context,
     bool has_force_restore_data_flag)
 {
-    using FileNames = std::vector<std::string>;
-    FileNames file_names;
-
-    DatabaseOnDisk::iterateTableFiles(*this, log, [&file_names](const String & file_name)
-    {
-        file_names.push_back(file_name);
-    });
-
-    if (file_names.empty())
-        return;
 
     /** Tables load faster if they are loaded in sorted (by name) order.
       * Otherwise (for the ext4 filesystem), `DirectoryIterator` iterates through them in some order,
       *  which does not correspond to order tables creation and does not correspond to order of their location on disk.
       */
-    std::sort(file_names.begin(), file_names.end());
+    using FileNames = std::map<std::string, ASTPtr>;
+    FileNames file_names;
 
-    const size_t total_tables = file_names.size();
-    LOG_INFO(log, "Total " << total_tables << " tables.");
+    size_t total_dictionaries = 0;
+    DatabaseOnDisk::iterateMetadataFiles(*this, log, [&file_names, &total_dictionaries, this](const String & file_name)
+    {
+        String full_path = metadata_path + "/" + file_name;
+        try
+        {
+            auto ast = parseCreateQueryFromMetadataFile(full_path, log);
+            if (ast)
+            {
+                auto * create_query = ast->as<ASTCreateQuery>();
+                file_names[file_name] = ast;
+                total_dictionaries += create_query->is_dictionary;
+            }
+        }
+        catch (const Exception & e)
+        {
+            throw Exception(
+                "Cannot parse definition from metadata file " + full_path + ", error: " + e.displayText() + ", stack trace:\n"
+                    + e.getStackTrace().toString(), ErrorCodes::CANNOT_PARSE_TEXT);
+        }
+
+    });
+
+    size_t total_tables = file_names.size() - total_dictionaries;
+
+    LOG_INFO(log, "Total " << total_tables << " tables and " << total_dictionaries << " dictionaries.");
 
     AtomicStopwatch watch;
-    std::atomic<size_t> tables_processed {0};
+    std::atomic<size_t> tables_processed{0};
+    std::atomic<size_t> dictionaries_processed{0};
 
-    auto loadOneTable = [&](const String & table)
+    auto loadOneObject = [&](const ASTCreateQuery & query)
     {
-        loadTable(context, getMetadataPath(), *this, getDatabaseName(), getDataPath(), table, has_force_restore_data_flag);
+        loadObject(context, query, *this, getDataPath(), getDatabaseName(), has_force_restore_data_flag);
 
         /// Messages, so that it's not boring to wait for the server to load for a long time.
-        if (++tables_processed % PRINT_MESSAGE_EACH_N_TABLES == 0
-            || watch.compareAndRestart(PRINT_MESSAGE_EACH_N_SECONDS))
-        {
-            LOG_INFO(log, std::fixed << std::setprecision(2) << tables_processed * 100.0 / total_tables << "%");
-            watch.restart();
-        }
+        if (query.is_dictionary)
+            logAboutProgress(log, ++dictionaries_processed, total_dictionaries, watch);
+        else
+            logAboutProgress(log, ++tables_processed, total_tables, watch);
     };
 
     ThreadPool pool(SettingMaxThreads().getAutoValue());
 
-    for (const auto & file_name : file_names)
+    for (const auto & name_with_query : file_names)
     {
-        pool.scheduleOrThrowOnError([&]() { loadOneTable(file_name); });
+        pool.scheduleOrThrowOnError([&]() { loadOneObject(name_with_query.second->as<const ASTCreateQuery &>()); });
     }
 
     pool.wait();
 
     /// After all tables was basically initialized, startup them.
     startupTables(pool);
+
+    /// Add database as repository
+    auto dictionaries_repository = std::make_unique<ExternalLoaderDatabaseConfigRepository>(shared_from_this(), context);
+    auto & external_loader = context.getExternalDictionariesLoader();
+    external_loader.addConfigRepository(getDatabaseName(), std::move(dictionaries_repository));
+    bool lazy_load = context.getConfigRef().getBool("dictionaries_lazy_load", true);
+    external_loader.reload(!lazy_load);
 }
 
 
@@ -160,18 +193,12 @@ void DatabaseOrdinary::startupTables(ThreadPool & thread_pool)
         return;
 
     AtomicStopwatch watch;
-    std::atomic<size_t> tables_processed {0};
+    std::atomic<size_t> tables_processed{0};
 
     auto startupOneTable = [&](const StoragePtr & table)
     {
         table->startup();
-
-        if (++tables_processed % PRINT_MESSAGE_EACH_N_TABLES == 0
-            || watch.compareAndRestart(PRINT_MESSAGE_EACH_N_SECONDS))
-        {
-            LOG_INFO(log, std::fixed << std::setprecision(2) << tables_processed * 100.0 / total_tables << "%");
-            watch.restart();
-        }
+        logAboutProgress(log, ++tables_processed, total_tables, watch);
     };
 
     try
@@ -187,7 +214,6 @@ void DatabaseOrdinary::startupTables(ThreadPool & thread_pool)
     thread_pool.wait();
 }
 
-
 void DatabaseOrdinary::createTable(
     const Context & context,
     const String & table_name,
@@ -197,6 +223,13 @@ void DatabaseOrdinary::createTable(
     DatabaseOnDisk::createTable(*this, context, table_name, table, query);
 }
 
+void DatabaseOrdinary::createDictionary(
+    const Context & context,
+    const String & dictionary_name,
+    const ASTPtr & query)
+{
+    DatabaseOnDisk::createDictionary(*this, context, dictionary_name, query);
+}
 
 void DatabaseOrdinary::removeTable(
     const Context & context,
@@ -205,6 +238,13 @@ void DatabaseOrdinary::removeTable(
     DatabaseOnDisk::removeTable(*this, context, table_name, log);
 }
 
+void DatabaseOrdinary::removeDictionary(
+    const Context & context,
+    const String & table_name)
+{
+    DatabaseOnDisk::removeDictionary(*this, context, table_name, log);
+}
+
 void DatabaseOrdinary::renameTable(
     const Context & context,
     const String & table_name,
@@ -216,11 +256,11 @@ void DatabaseOrdinary::renameTable(
 }
 
 
-time_t DatabaseOrdinary::getTableMetadataModificationTime(
+time_t DatabaseOrdinary::getObjectMetadataModificationTime(
     const Context & /* context */,
     const String & table_name)
 {
-    return DatabaseOnDisk::getTableMetadataModificationTime(*this, table_name);
+    return DatabaseOnDisk::getObjectMetadataModificationTime(*this, table_name);
 }
 
 ASTPtr DatabaseOrdinary::getCreateTableQuery(const Context & context, const String & table_name) const
@@ -233,6 +273,17 @@ ASTPtr DatabaseOrdinary::tryGetCreateTableQuery(const Context & context, const S
     return DatabaseOnDisk::tryGetCreateTableQuery(*this, context, table_name);
 }
 
+
+ASTPtr DatabaseOrdinary::getCreateDictionaryQuery(const Context & context, const String & dictionary_name) const
+{
+    return DatabaseOnDisk::getCreateDictionaryQuery(*this, context, dictionary_name);
+}
+
+ASTPtr DatabaseOrdinary::tryGetCreateDictionaryQuery(const Context & context, const String & dictionary_name) const
+{
+    return DatabaseOnDisk::tryGetCreateTableQuery(*this, context, dictionary_name);
+}
+
 ASTPtr DatabaseOrdinary::getCreateDatabaseQuery(const Context & context) const
 {
     return DatabaseOnDisk::getCreateDatabaseQuery(*this, context);
@@ -283,7 +334,7 @@ void DatabaseOrdinary::alterTable(
     if (storage_modifier)
         storage_modifier(*ast_create_query.storage);
 
-    statement = getTableDefinitionFromCreateQuery(ast);
+    statement = getObjectDefinitionFromCreateQuery(ast);
 
     {
         WriteBufferFromFile out(table_metadata_tmp_path, statement.size(), O_WRONLY | O_CREAT | O_EXCL);
@@ -328,9 +379,9 @@ String DatabaseOrdinary::getDatabaseName() const
     return name;
 }
 
-String DatabaseOrdinary::getTableMetadataPath(const String & table_name) const
+String DatabaseOrdinary::getObjectMetadataPath(const String & table_name) const
 {
-    return detail::getTableMetadataPath(getMetadataPath(), table_name);
+    return DatabaseOnDisk::getObjectMetadataPath(*this, table_name);
 }
 
 }

dbms/src/Databases/DatabaseOrdinary.h

@@ -18,7 +18,7 @@ public:
 
     String getEngineName() const override { return "Ordinary"; }
 
-    void loadTables(
+    void loadStoredObjects(
         Context & context,
         bool has_force_restore_data_flag) override;
 
@@ -28,10 +28,19 @@ public:
         const StoragePtr & table,
         const ASTPtr & query) override;
 
+    void createDictionary(
+        const Context & context,
+        const String & dictionary_name,
+        const ASTPtr & query) override;
+
     void removeTable(
         const Context & context,
         const String & table_name) override;
 
+    void removeDictionary(
+        const Context & context,
+        const String & table_name) override;
+
     void renameTable(
         const Context & context,
         const String & table_name,
@@ -47,7 +56,7 @@ public:
         const ConstraintsDescription & constraints,
         const ASTModifier & engine_modifier) override;
 
-    time_t getTableMetadataModificationTime(
+    time_t getObjectMetadataModificationTime(
         const Context & context,
         const String & table_name) override;
 
@@ -59,12 +68,20 @@ public:
         const Context & context,
         const String & table_name) const override;
 
+    ASTPtr tryGetCreateDictionaryQuery(
+        const Context & context,
+        const String & name) const override;
+
+    ASTPtr getCreateDictionaryQuery(
+        const Context & context,
+        const String & name) const override;
+
     ASTPtr getCreateDatabaseQuery(const Context & context) const override;
 
     String getDataPath() const override;
     String getDatabaseName() const override;
     String getMetadataPath() const override;
-    String getTableMetadataPath(const String & table_name) const override;
+    String getObjectMetadataPath(const String & table_name) const override;
 
     void drop() override;
 
@@ -74,8 +91,6 @@ private:
     Poco::Logger * log;
 
     void startupTables(ThreadPool & thread_pool);
-
-    ASTPtr getCreateTableQueryImpl(const Context & context, const String & table_name, bool throw_on_error) const;
 };
 
 }

dbms/src/Databases/DatabasesCommon.cpp

@@ -1,15 +1,20 @@
 #include <Databases/DatabasesCommon.h>
 
+#include <Interpreters/ExternalDictionariesLoader.h>
+#include <Interpreters/ExternalLoaderDatabaseConfigRepository.h>
 #include <Interpreters/Context.h>
 #include <Interpreters/InterpreterCreateQuery.h>
 #include <Parsers/ASTCreateQuery.h>
 #include <Parsers/ParserCreateQuery.h>
+#include <Parsers/ParserDictionary.h>
 #include <Parsers/formatAST.h>
 #include <Parsers/parseQuery.h>
 #include <Storages/IStorage.h>
+#include <Storages/StorageDictionary.h>
 #include <Storages/StorageFactory.h>
 #include <Common/typeid_cast.h>
 #include <TableFunctions/TableFunctionFactory.h>
+#include <Dictionaries/DictionaryFactory.h>
 
 #include <sstream>
 
@@ -23,115 +28,119 @@ namespace ErrorCodes
     extern const int TABLE_ALREADY_EXISTS;
     extern const int UNKNOWN_TABLE;
     extern const int LOGICAL_ERROR;
+    extern const int DICTIONARY_ALREADY_EXISTS;
 }
 
-
-String getTableDefinitionFromCreateQuery(const ASTPtr & query)
+namespace
 {
-    ASTPtr query_clone = query->clone();
-    auto & create = query_clone->as<ASTCreateQuery &>();
 
-    /// We remove everything that is not needed for ATTACH from the query.
-    create.attach = true;
-    create.database.clear();
-    create.as_database.clear();
-    create.as_table.clear();
-    create.if_not_exists = false;
-    create.is_populate = false;
-    create.replace_view = false;
-
-    /// For views it is necessary to save the SELECT query itself, for the rest - on the contrary
-    if (!create.is_view && !create.is_materialized_view && !create.is_live_view)
-        create.select = nullptr;
-
-    create.format = nullptr;
-    create.out_file = nullptr;
-
-    std::ostringstream statement_stream;
-    formatAST(create, statement_stream, false);
-    statement_stream << '\n';
-    return statement_stream.str();
-}
-
-
-std::pair<String, StoragePtr> createTableFromDefinition(
-    const String & definition,
-    const String & database_name,
-    const String & database_data_path,
-    Context & context,
-    bool has_force_restore_data_flag,
-    const String & description_for_error_message)
+StoragePtr getDictionaryStorage(const Context & context, const String & table_name, const String & db_name)
 {
-    ParserCreateQuery parser;
-    ASTPtr ast = parseQuery(parser, definition.data(), definition.data() + definition.size(), description_for_error_message, 0);
-
-    auto & ast_create_query = ast->as<ASTCreateQuery &>();
-    ast_create_query.attach = true;
-    ast_create_query.database = database_name;
-
-    if (ast_create_query.as_table_function)
+    auto dict_name = db_name + "." + table_name;
+    const auto & external_loader = context.getExternalDictionariesLoader();
+    auto dict_ptr = external_loader.tryGetDictionary(dict_name);
+    if (dict_ptr)
     {
-        const auto & table_function = ast_create_query.as_table_function->as<ASTFunction &>();
-        const auto & factory = TableFunctionFactory::instance();
-        StoragePtr storage = factory.get(table_function.name, context)->execute(ast_create_query.as_table_function, context, ast_create_query.table);
-        return {ast_create_query.table, storage};
+        const DictionaryStructure & dictionary_structure = dict_ptr->getStructure();
+        auto columns = StorageDictionary::getNamesAndTypes(dictionary_structure);
+        return StorageDictionary::create(db_name, table_name, ColumnsDescription{columns}, context, true, dict_name);
     }
-    /// We do not directly use `InterpreterCreateQuery::execute`, because
-    /// - the database has not been created yet;
-    /// - the code is simpler, since the query is already brought to a suitable form.
-    if (!ast_create_query.columns_list || !ast_create_query.columns_list->columns)
-        throw Exception("Missing definition of columns.", ErrorCodes::EMPTY_LIST_OF_COLUMNS_PASSED);
-
-    ColumnsDescription columns = InterpreterCreateQuery::getColumnsDescription(*ast_create_query.columns_list->columns, context);
-    ConstraintsDescription constraints = InterpreterCreateQuery::getConstraintsDescription(ast_create_query.columns_list->constraints);
-
-    return
-    {
-        ast_create_query.table,
-        StorageFactory::instance().get(
-            ast_create_query,
-            database_data_path, ast_create_query.table, database_name, context, context.getGlobalContext(),
-            columns, constraints,
-            true, has_force_restore_data_flag)
-    };
+    return nullptr;
 }
 
+}
 
 bool DatabaseWithOwnTablesBase::isTableExist(
     const Context & /*context*/,
     const String & table_name) const
 {
     std::lock_guard lock(mutex);
-    return tables.find(table_name) != tables.end();
+    return tables.find(table_name) != tables.end() || dictionaries.find(table_name) != dictionaries.end();
+}
+
+bool DatabaseWithOwnTablesBase::isDictionaryExist(
+    const Context & /*context*/,
+    const String & dictionary_name) const
+{
+    std::lock_guard lock(mutex);
+    return dictionaries.find(dictionary_name) != dictionaries.end();
 }
 
 StoragePtr DatabaseWithOwnTablesBase::tryGetTable(
-    const Context & /*context*/,
+    const Context & context,
     const String & table_name) const
 {
-    std::lock_guard lock(mutex);
-    auto it = tables.find(table_name);
-    if (it == tables.end())
-        return {};
-    return it->second;
+    {
+        std::lock_guard lock(mutex);
+        auto it = tables.find(table_name);
+        if (it != tables.end())
+            return it->second;
+    }
+
+    if (isDictionaryExist(context, table_name))
+        /// We don't need lock database here, because database doesn't store dictionary itself
+        /// just metadata
+        return getDictionaryStorage(context, table_name, getDatabaseName());
+
+    return {};
 }
 
-DatabaseIteratorPtr DatabaseWithOwnTablesBase::getIterator(const Context & /*context*/, const FilterByNameFunction & filter_by_table_name)
+DatabaseTablesIteratorPtr DatabaseWithOwnTablesBase::getTablesWithDictionaryTablesIterator(const Context & context, const FilterByNameFunction & filter_by_name)
+{
+    auto tables_it = getTablesIterator(context, filter_by_name);
+    auto dictionaries_it = getDictionariesIterator(context, filter_by_name);
+
+    Tables result;
+    while (tables_it && tables_it->isValid())
+    {
+        result.emplace(tables_it->name(), tables_it->table());
+        tables_it->next();
+    }
+
+    while (dictionaries_it && dictionaries_it->isValid())
+    {
+        auto table_name = dictionaries_it->name();
+        auto table_ptr = getDictionaryStorage(context, table_name, getDatabaseName());
+        if (table_ptr)
+            result.emplace(table_name, table_ptr);
+        dictionaries_it->next();
+    }
+
+    return std::make_unique<DatabaseTablesSnapshotIterator>(result);
+}
+
+DatabaseTablesIteratorPtr DatabaseWithOwnTablesBase::getTablesIterator(const Context & /*context*/, const FilterByNameFunction & filter_by_table_name)
 {
     std::lock_guard lock(mutex);
     if (!filter_by_table_name)
-        return std::make_unique<DatabaseSnapshotIterator>(tables);
+        return std::make_unique<DatabaseTablesSnapshotIterator>(tables);
+
     Tables filtered_tables;
     for (const auto & [table_name, storage] : tables)
         if (filter_by_table_name(table_name))
             filtered_tables.emplace(table_name, storage);
-    return std::make_unique<DatabaseSnapshotIterator>(std::move(filtered_tables));
+
+    return std::make_unique<DatabaseTablesSnapshotIterator>(std::move(filtered_tables));
+}
+
+
+DatabaseDictionariesIteratorPtr DatabaseWithOwnTablesBase::getDictionariesIterator(const Context & /*context*/, const FilterByNameFunction & filter_by_dictionary_name)
+{
+    std::lock_guard lock(mutex);
+    if (!filter_by_dictionary_name)
+        return std::make_unique<DatabaseDictionariesSnapshotIterator>(dictionaries);
+
+    Dictionaries filtered_dictionaries;
+    for (const auto & dictionary_name : dictionaries)
+        if (filter_by_dictionary_name(dictionary_name))
+            filtered_dictionaries.emplace(dictionary_name);
+    return std::make_unique<DatabaseDictionariesSnapshotIterator>(std::move(filtered_dictionaries));
 }
 
 bool DatabaseWithOwnTablesBase::empty(const Context & /*context*/) const
 {
     std::lock_guard lock(mutex);
-    return tables.empty();
+    return tables.empty() && dictionaries.empty();
 }
 
 StoragePtr DatabaseWithOwnTablesBase::detachTable(const String & table_name)
@@ -139,6 +148,9 @@ StoragePtr DatabaseWithOwnTablesBase::detachTable(const String & table_name)
     StoragePtr res;
     {
         std::lock_guard lock(mutex);
+        if (dictionaries.count(table_name))
+            throw Exception("Cannot detach dictionary " + name + "." + table_name + " as table, use DETACH DICTIONARY query.", ErrorCodes::UNKNOWN_TABLE);
+
         auto it = tables.find(table_name);
         if (it == tables.end())
             throw Exception("Table " + name + "." + table_name + " doesn't exist.", ErrorCodes::UNKNOWN_TABLE);
@@ -149,6 +161,21 @@ StoragePtr DatabaseWithOwnTablesBase::detachTable(const String & table_name)
     return res;
 }
 
+void DatabaseWithOwnTablesBase::detachDictionary(const String & dictionary_name, const Context & context, bool reload)
+{
+    {
+        std::lock_guard lock(mutex);
+        auto it = dictionaries.find(dictionary_name);
+        if (it == dictionaries.end())
+            throw Exception("Dictionary " + name + "." + dictionary_name + " doesn't exist.", ErrorCodes::UNKNOWN_TABLE);
+        dictionaries.erase(it);
+    }
+
+    if (reload)
+        context.getExternalDictionariesLoader().reload(getDatabaseName() + "." + dictionary_name);
+
+}
+
 void DatabaseWithOwnTablesBase::attachTable(const String & table_name, const StoragePtr & table)
 {
     std::lock_guard lock(mutex);
@@ -156,6 +183,25 @@ void DatabaseWithOwnTablesBase::attachTable(const String & table_name, const Sto
         throw Exception("Table " + name + "." + table_name + " already exists.", ErrorCodes::TABLE_ALREADY_EXISTS);
 }
 
+
+void DatabaseWithOwnTablesBase::attachDictionary(const String & dictionary_name, const Context & context, bool load)
+{
+    const auto & external_loader = context.getExternalDictionariesLoader();
+
+    String full_name = getDatabaseName() + "." + dictionary_name;
+    {
+        std::lock_guard lock(mutex);
+        auto status = external_loader.getCurrentStatus(full_name);
+        if (status != ExternalLoader::Status::NOT_EXIST || !dictionaries.emplace(dictionary_name).second)
+            throw Exception(
+                      "Dictionary " + full_name + " already exists.",
+                      ErrorCodes::DICTIONARY_ALREADY_EXISTS);
+    }
+
+    if (load)
+        external_loader.reload(full_name, true);
+}
+
 void DatabaseWithOwnTablesBase::shutdown()
 {
     /// You can not hold a lock during shutdown.
@@ -174,6 +220,7 @@ void DatabaseWithOwnTablesBase::shutdown()
 
     std::lock_guard lock(mutex);
     tables.clear();
+    dictionaries.clear();
 }
 
 DatabaseWithOwnTablesBase::~DatabaseWithOwnTablesBase()

dbms/src/Databases/DatabasesCommon.h

@@ -15,63 +15,6 @@ namespace DB
 
 class Context;
 
-
-/** Get the row with the table definition based on the CREATE query.
-  * It is an ATTACH query that you can execute to create a table from the correspondent database.
-  * See the implementation.
-  */
-String getTableDefinitionFromCreateQuery(const ASTPtr & query);
-
-
-/** Create a table by its definition, without using InterpreterCreateQuery.
-  *  (InterpreterCreateQuery has more complex functionality, and it can not be used if the database has not been created yet)
-  * Returns the table name and the table itself.
-  * You must subsequently call IStorage::startup method to use the table.
-  */
-std::pair<String, StoragePtr> createTableFromDefinition(
-    const String & definition,
-    const String & database_name,
-    const String & database_data_path,
-    Context & context,
-    bool has_force_restore_data_flag,
-    const String & description_for_error_message);
-
-
-/// Copies list of tables and iterates through such snapshot.
-class DatabaseSnapshotIterator final : public IDatabaseIterator
-{
-private:
-    Tables tables;
-    Tables::iterator it;
-
-public:
-    DatabaseSnapshotIterator(Tables & tables_)
-        : tables(tables_), it(tables.begin()) {}
-
-    DatabaseSnapshotIterator(Tables && tables_)
-        : tables(tables_), it(tables.begin()) {}
-
-    void next() override
-    {
-        ++it;
-    }
-
-    bool isValid() const override
-    {
-        return it != tables.end();
-    }
-
-    const String & name() const override
-    {
-        return it->first;
-    }
-
-    const StoragePtr & table() const override
-    {
-        return it->second;
-    }
-};
-
 /// A base class for databases that manage their own list of tables.
 class DatabaseWithOwnTablesBase : public IDatabase
 {
@@ -80,18 +23,27 @@ public:
         const Context & context,
         const String & table_name) const override;
 
+    bool isDictionaryExist(const Context & context, const String & dictionary_name) const override;
+
     StoragePtr tryGetTable(
         const Context & context,
         const String & table_name) const override;
 
     bool empty(const Context & context) const override;
 
-
     void attachTable(const String & table_name, const StoragePtr & table) override;
 
+    void attachDictionary(const String & name, const Context & context, bool reload) override;
+
     StoragePtr detachTable(const String & table_name) override;
 
-    DatabaseIteratorPtr getIterator(const Context & context, const FilterByNameFunction & filter_by_table_name = {}) override;
+    void detachDictionary(const String & name, const Context & context, bool reload) override;
+
+    DatabaseTablesIteratorPtr getTablesIterator(const Context & context, const FilterByNameFunction & filter_by_table_name = {}) override;
+
+    DatabaseDictionariesIteratorPtr getDictionariesIterator(const Context & context, const FilterByNameFunction & filter_by_dictionary_name = {}) override;
+
+    DatabaseTablesIteratorPtr getTablesWithDictionaryTablesIterator(const Context & context, const FilterByNameFunction & filter_by_dictionary_name = {}) override;
 
     void shutdown() override;
 
@@ -102,6 +54,7 @@ protected:
 
     mutable std::mutex mutex;
     Tables tables;
+    Dictionaries dictionaries;
 
     DatabaseWithOwnTablesBase(String name_) : name(std::move(name_)) { }
 };

dbms/src/Databases/IDatabase.h

@@ -3,6 +3,7 @@
 #include <Core/Types.h>
 #include <Parsers/IAST_fwd.h>
 #include <Storages/IStorage_fwd.h>
+#include <Dictionaries/IDictionary.h>
 #include <Common/Exception.h>
 
 #include <ctime>
@@ -19,16 +20,14 @@ struct ConstraintsDescription;
 class ColumnsDescription;
 struct IndicesDescription;
 struct TableStructureWriteLockHolder;
+using Dictionaries = std::set<String>;
 
 namespace ErrorCodes
 {
     extern const int NOT_IMPLEMENTED;
 }
 
-
-/** Allows to iterate over tables.
-  */
-class IDatabaseIterator
+class IDatabaseTablesIterator
 {
 public:
     virtual void next() = 0;
@@ -37,15 +36,57 @@ public:
     virtual const String & name() const = 0;
     virtual const StoragePtr & table() const = 0;
 
-    virtual ~IDatabaseIterator() {}
+    virtual ~IDatabaseTablesIterator() = default;
 };
 
-using DatabaseIteratorPtr = std::unique_ptr<IDatabaseIterator>;
+/// Copies list of tables and iterates through such snapshot.
+class DatabaseTablesSnapshotIterator : public IDatabaseTablesIterator
+{
+private:
+    Tables tables;
+    Tables::iterator it;
+
+public:
+    DatabaseTablesSnapshotIterator(Tables & tables_) : tables(tables_), it(tables.begin()) {}
+
+    DatabaseTablesSnapshotIterator(Tables && tables_) : tables(tables_), it(tables.begin()) {}
+
+    void next() { ++it; }
+
+    bool isValid() const { return it != tables.end(); }
+
+    const String & name() const { return it->first; }
+
+    const StoragePtr & table() const { return it->second; }
+};
+
+/// Copies list of dictionaries and iterates through such snapshot.
+class DatabaseDictionariesSnapshotIterator
+{
+private:
+    Dictionaries dictionaries;
+    Dictionaries::iterator it;
+
+public:
+    DatabaseDictionariesSnapshotIterator() = default;
+    DatabaseDictionariesSnapshotIterator(Dictionaries & dictionaries_) : dictionaries(dictionaries_), it(dictionaries.begin()) {}
+
+    DatabaseDictionariesSnapshotIterator(Dictionaries && dictionaries_) : dictionaries(dictionaries_), it(dictionaries.begin()) {}
+
+    void next() { ++it; }
+
+    bool isValid() const { return !dictionaries.empty() && it != dictionaries.end(); }
+
+    const String & name() const { return *it; }
+};
+
+using DatabaseTablesIteratorPtr = std::unique_ptr<IDatabaseTablesIterator>;
+using DatabaseDictionariesIteratorPtr = std::unique_ptr<DatabaseDictionariesSnapshotIterator>;
 
 
 /** Database engine.
   * It is responsible for:
-  * - initialization of set of known tables;
+  * - initialization of set of known tables and dictionaries;
   * - checking existence of a table and getting a table object;
   * - retrieving a list of all tables;
   * - creating and dropping tables;
@@ -60,7 +101,7 @@ public:
 
     /// Load a set of existing tables.
     /// You can call only once, right after the object is created.
-    virtual void loadTables(
+    virtual void loadStoredObjects(
         Context & context,
         bool has_force_restore_data_flag) = 0;
 
@@ -69,6 +110,11 @@ public:
         const Context & context,
         const String & name) const = 0;
 
+    /// Check the existence of the dictionary
+    virtual bool isDictionaryExist(
+        const Context & context,
+        const String & name) const = 0;
+
     /// Get the table for work. Return nullptr if there is no table.
     virtual StoragePtr tryGetTable(
         const Context & context,
@@ -78,7 +124,16 @@ public:
 
     /// Get an iterator that allows you to pass through all the tables.
     /// It is possible to have "hidden" tables that are not visible when passing through, but are visible if you get them by name using the functions above.
-    virtual DatabaseIteratorPtr getIterator(const Context & context, const FilterByNameFunction & filter_by_table_name = {}) = 0;
+    virtual DatabaseTablesIteratorPtr getTablesIterator(const Context & context, const FilterByNameFunction & filter_by_table_name = {}) = 0;
+
+    /// Get an iterator to pass through all the dictionaries.
+    virtual DatabaseDictionariesIteratorPtr getDictionariesIterator(const Context & context, const FilterByNameFunction & filter_by_dictionary_name = {}) = 0;
+
+    /// Get an iterator to pass through all the tables and dictionary tables.
+    virtual DatabaseTablesIteratorPtr getTablesWithDictionaryTablesIterator(const Context & context, const FilterByNameFunction & filter_by_name = {})
+    {
+        return getTablesIterator(context, filter_by_name);
+    }
 
     /// Is the database empty.
     virtual bool empty(const Context & context) const = 0;
@@ -90,17 +145,35 @@ public:
         const StoragePtr & table,
         const ASTPtr & query) = 0;
 
+    /// Add the dictionary to the database. Record its presence in the metadata.
+    virtual void createDictionary(
+        const Context & context,
+        const String & dictionary_name,
+        const ASTPtr & query) = 0;
+
     /// Delete the table from the database. Delete the metadata.
     virtual void removeTable(
         const Context & context,
         const String & name) = 0;
 
+    /// Delete the dictionary from the database. Delete the metadata.
+    virtual void removeDictionary(
+        const Context & context,
+        const String & dictionary_name) = 0;
+
     /// Add a table to the database, but do not add it to the metadata. The database may not support this method.
     virtual void attachTable(const String & name, const StoragePtr & table) = 0;
 
+    /// Add dictionary to the database, but do not add it to the metadata. The database may not support this method.
+    /// load is false when we starting up and lazy_load is true, so we don't want to load dictionaries synchronously.
+    virtual void attachDictionary(const String & name, const Context & context, bool reload = true) = 0;
+
     /// Forget about the table without deleting it, and return it. The database may not support this method.
     virtual StoragePtr detachTable(const String & name) = 0;
 
+    /// Forget about the dictionary without deleting it, and return it. The database may not support this method.
+    virtual void detachDictionary(const String & name, const Context & context, bool reload = true) = 0;
+
     /// Rename the table and possibly move the table to another database.
     virtual void renameTable(
         const Context & /*context*/,
@@ -128,7 +201,7 @@ public:
     }
 
     /// Returns time of table's metadata change, 0 if there is no corresponding metadata file.
-    virtual time_t getTableMetadataModificationTime(
+    virtual time_t getObjectMetadataModificationTime(
         const Context & context,
         const String & name) = 0;
 
@@ -140,6 +213,14 @@ public:
         return tryGetCreateTableQuery(context, name);
     }
 
+    /// Get the CREATE DICTIONARY query for the dictionary. Returns nullptr if dictionary doesn't exists.
+    virtual ASTPtr tryGetCreateDictionaryQuery(const Context & context, const String & name) const = 0;
+
+    virtual ASTPtr getCreateDictionaryQuery(const Context & context, const String & name) const
+    {
+        return tryGetCreateDictionaryQuery(context, name);
+    }
+
     /// Get the CREATE DATABASE query for current database.
     virtual ASTPtr getCreateDatabaseQuery(const Context & context) const = 0;
 
@@ -150,7 +231,7 @@ public:
     /// Returns metadata path if the database supports it, empty string otherwise
     virtual String getMetadataPath() const { return {}; }
     /// Returns metadata path of a concrete table if the database supports it, empty string otherwise
-    virtual String getTableMetadataPath(const String & /*table_name*/) const { return {}; }
+    virtual String getObjectMetadataPath(const String & /*table_name*/) const { return {}; }
 
     /// Ask all tables to complete the background threads they are using and delete all table objects.
     virtual void shutdown() = 0;

dbms/src/Dictionaries/CMakeLists.txt

@@ -11,8 +11,8 @@ generate_code(CacheDictionary_generate2 UInt8 UInt16 UInt32 UInt64 UInt128 Int8
 generate_code(CacheDictionary_generate3 UInt8 UInt16 UInt32 UInt64 UInt128 Int8 Int16 Int32 Int64 Float32 Float64 Decimal32 Decimal64 Decimal128)
 add_headers_and_sources(clickhouse_dictionaries ${CMAKE_CURRENT_BINARY_DIR}/generated/)
 
-list(REMOVE_ITEM clickhouse_dictionaries_sources DictionaryFactory.cpp DictionarySourceFactory.cpp DictionaryStructure.cpp)
-list(REMOVE_ITEM clickhouse_dictionaries_headers DictionaryFactory.h DictionarySourceFactory.h DictionaryStructure.h)
+list(REMOVE_ITEM clickhouse_dictionaries_sources DictionaryFactory.cpp DictionarySourceFactory.cpp DictionaryStructure.cpp getDictionaryConfigurationFromAST.cpp)
+list(REMOVE_ITEM clickhouse_dictionaries_headers DictionaryFactory.h DictionarySourceFactory.h DictionaryStructure.h getDictionaryConfigurationFromAST.h)
 
 add_library(clickhouse_dictionaries ${clickhouse_dictionaries_sources})
 target_link_libraries(clickhouse_dictionaries PRIVATE dbms clickhouse_common_io ${BTRIE_LIBRARIES})

dbms/src/Dictionaries/CacheDictionary.cpp

@@ -611,7 +611,7 @@ void registerDictionaryCache(DictionaryFactory & factory)
         const DictionaryLifetime dict_lifetime{config, config_prefix + ".lifetime"};
         return std::make_unique<CacheDictionary>(name, dict_struct, std::move(source_ptr), dict_lifetime, size);
     };
-    factory.registerLayout("cache", create_layout);
+    factory.registerLayout("cache", create_layout, false);
 }
 
 

dbms/src/Dictionaries/ClickHouseDictionarySource.cpp

@@ -52,7 +52,7 @@ ClickHouseDictionarySource::ClickHouseDictionarySource(
     const Poco::Util::AbstractConfiguration & config,
     const std::string & config_prefix,
     const Block & sample_block_,
-    Context & context_)
+    const Context & context_)
     : update_time{std::chrono::system_clock::from_time_t(0)}
     , dict_struct{dict_struct_}
     , host{config.getString(config_prefix + ".host")}
@@ -206,7 +206,7 @@ void registerDictionarySourceClickHouse(DictionarySourceFactory & factory)
                                  const Poco::Util::AbstractConfiguration & config,
                                  const std::string & config_prefix,
                                  Block & sample_block,
-                                 Context & context) -> DictionarySourcePtr
+                                 const Context & context) -> DictionarySourcePtr
     {
         return std::make_unique<ClickHouseDictionarySource>(dict_struct, config, config_prefix + ".clickhouse", sample_block, context);
     };

dbms/src/Dictionaries/ClickHouseDictionarySource.h

@@ -23,7 +23,7 @@ public:
         const Poco::Util::AbstractConfiguration & config,
         const std::string & config_prefix,
         const Block & sample_block_,
-        Context & context);
+        const Context & context);
 
     /// copy-constructor is provided in order to support cloneability
     ClickHouseDictionarySource(const ClickHouseDictionarySource & other);

dbms/src/Dictionaries/ComplexKeyCacheDictionary.cpp

@@ -415,7 +415,7 @@ void registerDictionaryComplexKeyCache(DictionaryFactory & factory)
         const DictionaryLifetime dict_lifetime{config, config_prefix + ".lifetime"};
         return std::make_unique<ComplexKeyCacheDictionary>(name, dict_struct, std::move(source_ptr), dict_lifetime, size);
     };
-    factory.registerLayout("complex_key_cache", create_layout);
+    factory.registerLayout("complex_key_cache", create_layout, true);
 }
 
 

dbms/src/Dictionaries/ComplexKeyHashedDictionary.cpp

@@ -755,7 +755,7 @@ void registerDictionaryComplexKeyHashed(DictionaryFactory & factory)
         const bool require_nonempty = config.getBool(config_prefix + ".require_nonempty", false);
         return std::make_unique<ComplexKeyHashedDictionary>(name, dict_struct, std::move(source_ptr), dict_lifetime, require_nonempty);
     };
-    factory.registerLayout("complex_key_hashed", create_layout);
+    factory.registerLayout("complex_key_hashed", create_layout, true);
 }
 
 

dbms/src/Dictionaries/DictionaryFactory.cpp

@@ -3,6 +3,7 @@
 #include <memory>
 #include "DictionarySourceFactory.h"
 #include "DictionaryStructure.h"
+#include "getDictionaryConfigurationFromAST.h"
 
 namespace DB
 {
@@ -12,15 +13,21 @@ namespace ErrorCodes
     extern const int UNKNOWN_ELEMENT_IN_CONFIG;
 }
 
-void DictionaryFactory::registerLayout(const std::string & layout_type, Creator create_layout)
+void DictionaryFactory::registerLayout(const std::string & layout_type, Creator create_layout, bool is_complex)
 {
     if (!registered_layouts.emplace(layout_type, std::move(create_layout)).second)
         throw Exception("DictionaryFactory: the layout name '" + layout_type + "' is not unique", ErrorCodes::LOGICAL_ERROR);
+
+    layout_complexity[layout_type] = is_complex;
+
 }
 
 
 DictionaryPtr DictionaryFactory::create(
-    const std::string & name, const Poco::Util::AbstractConfiguration & config, const std::string & config_prefix, Context & context) const
+    const std::string & name,
+    const Poco::Util::AbstractConfiguration & config,
+    const std::string & config_prefix,
+    const Context & context) const
 {
     Poco::Util::AbstractConfiguration::Keys keys;
     const auto & layout_prefix = config_prefix + ".layout";
@@ -31,7 +38,7 @@ DictionaryPtr DictionaryFactory::create(
 
     const DictionaryStructure dict_struct{config, config_prefix + ".structure"};
 
-    auto source_ptr = DictionarySourceFactory::instance().create(name, config, config_prefix + ".source", dict_struct, context);
+    DictionarySourcePtr source_ptr = DictionarySourceFactory::instance().create(name, config, config_prefix + ".source", dict_struct, context);
 
     const auto & layout_type = keys.front();
 
@@ -39,14 +46,21 @@ DictionaryPtr DictionaryFactory::create(
         const auto found = registered_layouts.find(layout_type);
         if (found != registered_layouts.end())
         {
-            const auto & create_layout = found->second;
-            return create_layout(name, dict_struct, config, config_prefix, std::move(source_ptr));
+            const auto & layout_creator = found->second;
+            return layout_creator(name, dict_struct, config, config_prefix, std::move(source_ptr));
         }
     }
 
     throw Exception{name + ": unknown dictionary layout type: " + layout_type, ErrorCodes::UNKNOWN_ELEMENT_IN_CONFIG};
 }
 
+DictionaryPtr DictionaryFactory::create(const std::string & name, const ASTCreateQuery & ast, const Context & context) const
+{
+    auto configurationFromAST = getDictionaryConfigurationFromAST(ast);
+    return DictionaryFactory::create(name, *configurationFromAST, "dictionary", context);
+}
+
+
 DictionaryFactory & DictionaryFactory::instance()
 {
     static DictionaryFactory ret;

dbms/src/Dictionaries/DictionaryFactory.h

@@ -1,6 +1,7 @@
 #pragma once
 
 #include "IDictionary.h"
+#include <Parsers/ASTCreateQuery.h>
 
 
 namespace Poco
@@ -27,7 +28,15 @@ public:
 
     static DictionaryFactory & instance();
 
-    DictionaryPtr create(const std::string & name, const Poco::Util::AbstractConfiguration & config, const std::string & config_prefix, Context & context) const;
+    DictionaryPtr create(
+        const std::string & name,
+        const Poco::Util::AbstractConfiguration & config,
+        const std::string & config_prefix,
+        const Context & context) const;
+
+    DictionaryPtr create(const std::string & name,
+        const ASTCreateQuery & ast,
+        const Context & context) const;
 
     using Creator = std::function<DictionaryPtr(
         const std::string & name,
@@ -36,11 +45,15 @@ public:
         const std::string & config_prefix,
         DictionarySourcePtr source_ptr)>;
 
-    void registerLayout(const std::string & layout_type, Creator create_layout);
+    bool isComplex(const std::string & layout_type) const { return layout_complexity.at(layout_type); }
+
+    void registerLayout(const std::string & layout_type, Creator create_layout, bool is_complex);
 
 private:
     using LayoutRegistry = std::unordered_map<std::string, Creator>;
     LayoutRegistry registered_layouts;
+    using LayoutComplexity = std::unordered_map<std::string, bool>;
+    LayoutComplexity layout_complexity;
 };
 
 }

dbms/src/Dictionaries/DictionarySourceFactory.cpp

@@ -80,7 +80,7 @@ DictionarySourcePtr DictionarySourceFactory::create(
     const Poco::Util::AbstractConfiguration & config,
     const std::string & config_prefix,
     const DictionaryStructure & dict_struct,
-    Context & context) const
+    const Context & context) const
 {
     Poco::Util::AbstractConfiguration::Keys keys;
     config.keys(config_prefix, keys);

dbms/src/Dictionaries/DictionarySourceFactory.h

@@ -31,7 +31,7 @@ public:
         const Poco::Util::AbstractConfiguration & config,
         const std::string & config_prefix,
         Block & sample_block,
-        Context & context)>;
+        const Context & context)>;
 
     DictionarySourceFactory();
 
@@ -42,7 +42,7 @@ public:
         const Poco::Util::AbstractConfiguration & config,
         const std::string & config_prefix,
         const DictionaryStructure & dict_struct,
-        Context & context) const;
+        const Context & context) const;
 
 private:
     using SourceRegistry = std::unordered_map<std::string, Creator>;

dbms/src/Dictionaries/ExecutableDictionarySource.cpp

@@ -217,7 +217,7 @@ void registerDictionarySourceExecutable(DictionarySourceFactory & factory)
                                  const Poco::Util::AbstractConfiguration & config,
                                  const std::string & config_prefix,
                                  Block & sample_block,
-                                 Context & context) -> DictionarySourcePtr
+                                 const Context & context) -> DictionarySourcePtr
     {
         if (dict_struct.has_expressions)
             throw Exception{"Dictionary source of type `executable` does not support attribute expressions", ErrorCodes::LOGICAL_ERROR};

dbms/src/Dictionaries/FileDictionarySource.cpp

@@ -56,7 +56,7 @@ void registerDictionarySourceFile(DictionarySourceFactory & factory)
                                  const Poco::Util::AbstractConfiguration & config,
                                  const std::string & config_prefix,
                                  Block & sample_block,
-                                 Context & context) -> DictionarySourcePtr
+                                 const Context & context) -> DictionarySourcePtr
     {
         if (dict_struct.has_expressions)
             throw Exception{"Dictionary source of type `file` does not support attribute expressions", ErrorCodes::LOGICAL_ERROR};

dbms/src/Dictionaries/FlatDictionary.cpp

@@ -724,7 +724,7 @@ void registerDictionaryFlat(DictionaryFactory & factory)
         const bool require_nonempty = config.getBool(config_prefix + ".require_nonempty", false);
         return std::make_unique<FlatDictionary>(name, dict_struct, std::move(source_ptr), dict_lifetime, require_nonempty);
     };
-    factory.registerLayout("flat", create_layout);
+    factory.registerLayout("flat", create_layout, false);
 }
 
 

dbms/src/Dictionaries/HTTPDictionarySource.cpp

@@ -188,7 +188,7 @@ void registerDictionarySourceHTTP(DictionarySourceFactory & factory)
                                  const Poco::Util::AbstractConfiguration & config,
                                  const std::string & config_prefix,
                                  Block & sample_block,
-                                 Context & context) -> DictionarySourcePtr
+                                 const Context & context) -> DictionarySourcePtr
     {
         if (dict_struct.has_expressions)
             throw Exception{"Dictionary source of type `http` does not support attribute expressions", ErrorCodes::LOGICAL_ERROR};

dbms/src/Dictionaries/HashedDictionary.cpp

@@ -787,8 +787,8 @@ void registerDictionaryHashed(DictionaryFactory & factory)
         const bool sparse = name == "sparse_hashed";
         return std::make_unique<HashedDictionary>(name, dict_struct, std::move(source_ptr), dict_lifetime, require_nonempty, sparse);
     };
-    factory.registerLayout("hashed", create_layout);
-    factory.registerLayout("sparse_hashed", create_layout);
+    factory.registerLayout("hashed", create_layout, false);
+    factory.registerLayout("sparse_hashed", create_layout, false);
 }
 
 }

dbms/src/Dictionaries/RangeHashedDictionary.cpp

@@ -691,7 +691,7 @@ void registerDictionaryRangeHashed(DictionaryFactory & factory)
         const bool require_nonempty = config.getBool(config_prefix + ".require_nonempty", false);
         return std::make_unique<RangeHashedDictionary>(name, dict_struct, std::move(source_ptr), dict_lifetime, require_nonempty);
     };
-    factory.registerLayout("range_hashed", create_layout);
+    factory.registerLayout("range_hashed", create_layout, false);
 }
 
 }

dbms/src/Dictionaries/TrieDictionary.cpp

@@ -767,7 +767,7 @@ void registerDictionaryTrie(DictionaryFactory & factory)
         // This is specialised trie for storing IPv4 and IPv6 prefixes.
         return std::make_unique<TrieDictionary>(name, dict_struct, std::move(source_ptr), dict_lifetime, require_nonempty);
     };
-    factory.registerLayout("ip_trie", create_layout);
+    factory.registerLayout("ip_trie", create_layout, true);
 }
 
 }

dbms/src/Dictionaries/XDBCDictionarySource.cpp

@@ -238,7 +238,7 @@ void registerDictionarySourceXDBC(DictionarySourceFactory & factory)
                                  const Poco::Util::AbstractConfiguration & config,
                                  const std::string & config_prefix,
                                  Block & sample_block,
-                                 Context & context) -> DictionarySourcePtr {
+                                 const Context & context) -> DictionarySourcePtr {
 #if USE_POCO_SQLODBC || USE_POCO_DATAODBC
         BridgeHelperPtr bridge = std::make_shared<XDBCBridgeHelper<ODBCBridgeMixin>>(
             context, context.getSettings().http_receive_timeout, config.getString(config_prefix + ".odbc.connection_string"));

dbms/src/Dictionaries/getDictionaryConfigurationFromAST.cpp

@@ -0,0 +1,444 @@
+#include <Dictionaries/getDictionaryConfigurationFromAST.h>
+
+#include <Poco/DOM/AutoPtr.h>
+#include <Poco/DOM/Document.h>
+#include <Poco/DOM/Element.h>
+#include <Poco/DOM/Text.h>
+#include <Poco/Util/AbstractConfiguration.h>
+#include <Poco/Util/XMLConfiguration.h>
+#include <IO/WriteHelpers.h>
+#include <Parsers/queryToString.h>
+#include <Parsers/ASTIdentifier.h>
+#include <Parsers/ASTFunction.h>
+#include <Core/Names.h>
+#include <Parsers/ASTFunctionWithKeyValueArguments.h>
+#include <Parsers/ASTDictionaryAttributeDeclaration.h>
+#include <Dictionaries/DictionaryFactory.h>
+
+namespace DB
+{
+
+namespace ErrorCodes
+{
+    extern const int INCORRECT_DICTIONARY_DEFINITION;
+}
+
+/// There are a lot of code, but it's very simple and straightforward
+/// We just convert
+namespace
+{
+
+/// Get value from field and convert it to string.
+/// Also remove quotes from strings.
+String getUnescapedFieldString(const Field & field)
+{
+    String string = applyVisitor(FieldVisitorToString(), field);
+    if (!string.empty() && string.front() == '\'' && string.back() == '\'')
+        return string.substr(1, string.size() - 2);
+    return string;
+}
+
+
+using namespace Poco;
+using namespace Poco::XML;
+/*
+ * Transforms next definition
+ *  LIFETIME(MIN 10, MAX 100)
+ * to the next configuration
+ *  <lifetime>
+ *    <min>10</min>
+ *    <max>100</max>
+ *  </lifetime>
+ */
+void buildLifetimeConfiguration(
+    AutoPtr<Document> doc,
+    AutoPtr<Element> root,
+    const ASTDictionaryLifetime * lifetime)
+{
+
+    AutoPtr<Element> lifetime_element(doc->createElement("lifetime"));
+    AutoPtr<Element> min_element(doc->createElement("min"));
+    AutoPtr<Element> max_element(doc->createElement("max"));
+    AutoPtr<Text> min_sec(doc->createTextNode(toString(lifetime->min_sec)));
+    min_element->appendChild(min_sec);
+    AutoPtr<Text> max_sec(doc->createTextNode(toString(lifetime->max_sec)));
+    max_element->appendChild(max_sec);
+    lifetime_element->appendChild(min_element);
+    lifetime_element->appendChild(max_element);
+    root->appendChild(lifetime_element);
+}
+
+/*
+ * Transforms next definition
+ *  LAYOUT(FLAT())
+ * to the next configuration
+ *  <layout>
+ *    <flat/>
+ *  </layout>
+ *
+ * And next definition
+ *  LAYOUT(CACHE(SIZE_IN_CELLS 1000))
+ * to the next one
+ *  <layout>
+ *    <cache>
+ *      <size_in_cells>1000</size_in_cells>
+ *    </cache>
+ *  </layout>
+ */
+void buildLayoutConfiguration(
+    AutoPtr<Document> doc,
+    AutoPtr<Element> root,
+    const ASTDictionaryLayout * layout)
+{
+    AutoPtr<Element> layout_element(doc->createElement("layout"));
+    root->appendChild(layout_element);
+    AutoPtr<Element> layout_type_element(doc->createElement(layout->layout_type));
+    layout_element->appendChild(layout_type_element);
+    if (layout->parameter.has_value())
+    {
+        const auto & param = layout->parameter;
+        AutoPtr<Element> layout_type_parameter_element(doc->createElement(param->first));
+        const ASTLiteral & literal = param->second->as<const ASTLiteral &>();
+        AutoPtr<Text> value(doc->createTextNode(toString(literal.value.get<UInt64>())));
+        layout_type_parameter_element->appendChild(value);
+        layout_type_element->appendChild(layout_type_parameter_element);
+    }
+}
+
+/*
+ * Transforms next definition
+ *  RANGE(MIN StartDate, MAX EndDate)
+ * to the next configuration
+ *  <range_min><name>StartDate</name></range_min>
+ *  <range_max><name>EndDate</name></range_max>
+ */
+void buildRangeConfiguration(AutoPtr<Document> doc, AutoPtr<Element> root, const ASTDictionaryRange * range)
+{
+    // appends <key><name>value</name></key> to root
+    auto appendElem = [&doc, &root](const std::string & key, const std::string & value)
+    {
+        AutoPtr<Element> element(doc->createElement(key));
+        AutoPtr<Element> name(doc->createElement("name"));
+        AutoPtr<Text> text(doc->createTextNode(value));
+        name->appendChild(text);
+        element->appendChild(name);
+        root->appendChild(element);
+    };
+
+    appendElem("range_min", range->min_attr_name);
+    appendElem("range_max", range->max_attr_name);
+}
+
+
+/// Get primary key columns names from AST
+Names getPrimaryKeyColumns(const ASTExpressionList * primary_key)
+{
+    Names result;
+    const auto & children = primary_key->children;
+
+    for (size_t index = 0; index != children.size(); ++index)
+    {
+        const ASTIdentifier * key_part = children[index]->as<const ASTIdentifier>();
+        result.push_back(key_part->name);
+    }
+    return result;
+}
+
+/**
+  * Transofrms single dictionary attribute to configuration
+  *  third_column UInt8 DEFAULT 2 EXPRESSION rand() % 100 * 77
+  * to
+  *  <attribute>
+  *      <name>third_column</name>
+  *      <type>UInt8</type>
+  *      <null_value>2</null_value>
+  *      <expression>(rand() % 100) * 77</expression>
+  *  </attribute>
+  */
+void buildSingleAttribute(
+    AutoPtr<Document> doc,
+    AutoPtr<Element> root,
+    const ASTDictionaryAttributeDeclaration * dict_attr)
+{
+    AutoPtr<Element> attribute_element(doc->createElement("attribute"));
+    root->appendChild(attribute_element);
+
+    AutoPtr<Element> name_element(doc->createElement("name"));
+    AutoPtr<Text> name(doc->createTextNode(dict_attr->name));
+    name_element->appendChild(name);
+    attribute_element->appendChild(name_element);
+
+    AutoPtr<Element> type_element(doc->createElement("type"));
+    AutoPtr<Text> type(doc->createTextNode(queryToString(dict_attr->type)));
+    type_element->appendChild(type);
+    attribute_element->appendChild(type_element);
+
+     AutoPtr<Element> null_value_element(doc->createElement("null_value"));
+     String null_value_str;
+     if (dict_attr->default_value)
+         null_value_str = queryToString(dict_attr->default_value);
+     AutoPtr<Text> null_value(doc->createTextNode(null_value_str));
+     null_value_element->appendChild(null_value);
+     attribute_element->appendChild(null_value_element);
+
+    if (dict_attr->expression != nullptr)
+    {
+        AutoPtr<Element> expression_element(doc->createElement("expression"));
+        AutoPtr<Text> expression(doc->createTextNode(queryToString(dict_attr->expression)));
+        expression_element->appendChild(expression);
+        attribute_element->appendChild(expression_element);
+    }
+
+    if (dict_attr->hierarchical)
+    {
+        AutoPtr<Element> hierarchical_element(doc->createElement("hierarchical"));
+        AutoPtr<Text> hierarchical(doc->createTextNode("true"));
+        hierarchical_element->appendChild(hierarchical);
+        attribute_element->appendChild(hierarchical_element);
+    }
+
+    if (dict_attr->injective)
+    {
+        AutoPtr<Element> injective_element(doc->createElement("injective"));
+        AutoPtr<Text> injective(doc->createTextNode("true"));
+        injective_element->appendChild(injective);
+        attribute_element->appendChild(injective_element);
+    }
+
+    if (dict_attr->is_object_id)
+    {
+        AutoPtr<Element> is_object_id_element(doc->createElement("is_object_id"));
+        AutoPtr<Text> is_object_id(doc->createTextNode("true"));
+        is_object_id_element->appendChild(is_object_id);
+        attribute_element->appendChild(is_object_id_element);
+    }
+}
+
+
+/**
+  * Transforms
+  *   PRIMARY KEY Attr1 ,..., AttrN
+  * to the next configuration
+  *  <id><name>Attr1</name></id>
+  * or
+  *  <key>
+  *    <attribute>
+  *        <name>Attr1</name>
+  *        <type>UInt8</type>
+  *    </attribute>
+  *    ...
+  *    <attribute> fe
+  *  </key>
+  *
+  */
+void buildPrimaryKeyConfiguration(
+    AutoPtr<Document> doc,
+    AutoPtr<Element> root,
+    bool complex,
+    const Names & key_names,
+    const ASTExpressionList * dictionary_attributes)
+{
+    if (!complex)
+    {
+        if (key_names.size() != 1)
+            throw Exception("Primary key for simple dictionary must contain exactly one element",
+                ErrorCodes::INCORRECT_DICTIONARY_DEFINITION);
+
+        AutoPtr<Element> id_element(doc->createElement("id"));
+        root->appendChild(id_element);
+        AutoPtr<Element> name_element(doc->createElement("name"));
+        id_element->appendChild(name_element);
+        AutoPtr<Text> name(doc->createTextNode(*key_names.begin()));
+        name_element->appendChild(name);
+    }
+    else
+    {
+        const auto & children = dictionary_attributes->children;
+        if (children.size() < key_names.size())
+            throw Exception(
+                "Primary key fields count is more, than dictionary attributes count.", ErrorCodes::INCORRECT_DICTIONARY_DEFINITION);
+
+        AutoPtr<Element> key_element(doc->createElement("key"));
+        root->appendChild(key_element);
+        for (const auto & key_name : key_names)
+        {
+            bool found = false;
+            for (const auto & attr : children)
+            {
+                const ASTDictionaryAttributeDeclaration * dict_attr = attr->as<const ASTDictionaryAttributeDeclaration>();
+                if (dict_attr->name == key_name)
+                {
+                    found = true;
+                    buildSingleAttribute(doc, key_element, dict_attr);
+                    break;
+                }
+            }
+            if (!found)
+                throw Exception(
+                    "Primary key field '" + key_name + "' not found among attributes.", ErrorCodes::INCORRECT_DICTIONARY_DEFINITION);
+        }
+    }
+}
+
+
+/**
+  * Transforms list of ASTDictionaryAttributeDeclarations to list of dictionary attributes
+  */
+std::unordered_set<std::string> buildDictionaryAttributesConfiguration(
+    AutoPtr<Document> doc,
+    AutoPtr<Element> root,
+    const ASTExpressionList * dictionary_attributes,
+    const Names & key_columns)
+{
+    const auto & children = dictionary_attributes->children;
+    std::unordered_set<std::string> dictionary_attributes_names;
+    for (size_t i = 0; i < children.size(); ++i)
+    {
+        const ASTDictionaryAttributeDeclaration * dict_attr = children[i]->as<const ASTDictionaryAttributeDeclaration>();
+        if (!dict_attr->type)
+            throw Exception("Dictionary attribute must has type", ErrorCodes::INCORRECT_DICTIONARY_DEFINITION);
+
+        dictionary_attributes_names.insert(dict_attr->name);
+        if (std::find(key_columns.begin(), key_columns.end(), dict_attr->name) == key_columns.end())
+            buildSingleAttribute(doc, root, dict_attr);
+    }
+    return dictionary_attributes_names;
+}
+
+/** Transform function with key-value arguments to configuration
+  * (used for source transformation)
+  */
+void buildConfigurationFromFunctionWithKeyValueArguments(
+    AutoPtr<Document> doc,
+    AutoPtr<Element> root,
+    const ASTExpressionList * ast_expr_list)
+{
+    const auto & children = ast_expr_list->children;
+    for (size_t i = 0; i != children.size(); ++i)
+    {
+        const ASTPair * pair = children[i]->as<const ASTPair>();
+        AutoPtr<Element> current_xml_element(doc->createElement(pair->first));
+        root->appendChild(current_xml_element);
+
+        if (auto identifier = pair->second->as<const ASTIdentifier>(); identifier)
+        {
+            AutoPtr<Text> value(doc->createTextNode(identifier->name));
+            current_xml_element->appendChild(value);
+        }
+        else if (auto literal = pair->second->as<const ASTLiteral>(); literal)
+        {
+            AutoPtr<Text> value(doc->createTextNode(getUnescapedFieldString(literal->value)));
+            current_xml_element->appendChild(value);
+        }
+        else if (auto list = pair->second->as<const ASTExpressionList>(); list)
+        {
+            buildConfigurationFromFunctionWithKeyValueArguments(doc, current_xml_element, list);
+        }
+        else
+        {
+            throw Exception(
+                "Incorrect ASTPair contains wrong value, should be literal, identifier or list",
+                ErrorCodes::INCORRECT_DICTIONARY_DEFINITION);
+        }
+    }
+}
+
+/** Build source definition from ast.
+  *   SOURCE(MYSQL(HOST 'localhost' PORT 9000 USER 'default' REPLICA(HOST '127.0.0.1' PRIORITY 1) PASSWORD ''))
+  * to
+  *   <source>
+  *       <mysql>
+  *           <host>localhost</host>
+  *           ...
+  *           <replica>
+  *               <host>127.0.0.1</host>
+  *               ...
+  *           </replica>
+  *       </mysql>
+  *   </source>
+  */
+void buildSourceConfiguration(AutoPtr<Document> doc, AutoPtr<Element> root, const ASTFunctionWithKeyValueArguments * source)
+{
+    AutoPtr<Element> outer_element(doc->createElement("source"));
+    root->appendChild(outer_element);
+    AutoPtr<Element> source_element(doc->createElement(source->name));
+    outer_element->appendChild(source_element);
+    buildConfigurationFromFunctionWithKeyValueArguments(doc, source_element, source->elements->as<const ASTExpressionList>());
+}
+
+/** Check all AST fields are filled, throws exception
+  * in other case
+  */
+void checkAST(const ASTCreateQuery & query)
+{
+    if (!query.is_dictionary || query.dictionary == nullptr)
+        throw Exception("Cannot convert dictionary to configuration from non-dictionary AST.", ErrorCodes::INCORRECT_DICTIONARY_DEFINITION);
+
+    if (query.dictionary_attributes_list == nullptr || query.dictionary_attributes_list->children.empty())
+        throw Exception("Cannot create dictionary with empty attributes list", ErrorCodes::INCORRECT_DICTIONARY_DEFINITION);
+
+    if (query.dictionary->layout == nullptr)
+        throw Exception("Cannot create dictionary with empty layout", ErrorCodes::INCORRECT_DICTIONARY_DEFINITION);
+
+    if (query.dictionary->lifetime == nullptr)
+        throw Exception("Cannot create dictionary with empty lifetime", ErrorCodes::INCORRECT_DICTIONARY_DEFINITION);
+
+    if (query.dictionary->primary_key == nullptr)
+        throw Exception("Cannot create dictionary without primary key", ErrorCodes::INCORRECT_DICTIONARY_DEFINITION);
+
+    if (query.dictionary->source == nullptr)
+        throw Exception("Cannot create dictionary with empty source", ErrorCodes::INCORRECT_DICTIONARY_DEFINITION);
+
+    /// Range can be empty
+}
+
+void checkPrimaryKey(const std::unordered_set<std::string> & all_attrs, const Names & key_attrs)
+{
+    for (const auto & key_attr : key_attrs)
+        if (all_attrs.count(key_attr) == 0)
+            throw Exception("Unknown key attribute '" + key_attr + "'", ErrorCodes::INCORRECT_DICTIONARY_DEFINITION);
+}
+
+}
+
+
+DictionaryConfigurationPtr getDictionaryConfigurationFromAST(const ASTCreateQuery & query)
+{
+    checkAST(query);
+
+    AutoPtr<Poco::XML::Document> xml_document(new Poco::XML::Document());
+    AutoPtr<Poco::XML::Element> document_root(xml_document->createElement("dictionaries"));
+    xml_document->appendChild(document_root);
+    AutoPtr<Poco::XML::Element> current_dictionary(xml_document->createElement("dictionary"));
+    document_root->appendChild(current_dictionary);
+    AutoPtr<Poco::Util::XMLConfiguration> conf(new Poco::Util::XMLConfiguration());
+
+    AutoPtr<Poco::XML::Element> name_element(xml_document->createElement("name"));
+    current_dictionary->appendChild(name_element);
+    AutoPtr<Text> name(xml_document->createTextNode(query.database + "." + query.table));
+    name_element->appendChild(name);
+
+    AutoPtr<Element> structure_element(xml_document->createElement("structure"));
+    current_dictionary->appendChild(structure_element);
+    Names pk_attrs = getPrimaryKeyColumns(query.dictionary->primary_key);
+    auto dictionary_layout = query.dictionary->layout;
+
+    bool complex = DictionaryFactory::instance().isComplex(dictionary_layout->layout_type);
+
+    auto all_attr_names = buildDictionaryAttributesConfiguration(xml_document, structure_element, query.dictionary_attributes_list, pk_attrs);
+    checkPrimaryKey(all_attr_names, pk_attrs);
+
+    buildPrimaryKeyConfiguration(xml_document, structure_element, complex, pk_attrs, query.dictionary_attributes_list);
+
+    buildLayoutConfiguration(xml_document, current_dictionary, dictionary_layout);
+    buildSourceConfiguration(xml_document, current_dictionary, query.dictionary->source);
+    buildLifetimeConfiguration(xml_document, current_dictionary, query.dictionary->lifetime);
+
+    if (query.dictionary->range)
+        buildRangeConfiguration(xml_document, structure_element, query.dictionary->range);
+
+    conf->load(xml_document);
+    return conf;
+}
+
+}

dbms/src/Dictionaries/getDictionaryConfigurationFromAST.h

@@ -0,0 +1,15 @@
+#pragma once
+
+#include <Poco/Util/AbstractConfiguration.h>
+#include <Parsers/ASTCreateQuery.h>
+
+namespace DB
+{
+using DictionaryConfigurationPtr = Poco::AutoPtr<Poco::Util::AbstractConfiguration>;
+
+/// Convert dictionary AST to Poco::AbstractConfiguration
+/// This function is necessary because all loadable objects configuration are Poco::AbstractConfiguration
+/// Can throw exception if query is ill-formed
+DictionaryConfigurationPtr getDictionaryConfigurationFromAST(const ASTCreateQuery & query);
+
+}

dbms/src/Dictionaries/tests/gtest_dictionary_configuration.cpp

@@ -0,0 +1,224 @@
+#include <iostream>
+
+#include <sstream>
+#include <Core/Types.h>
+#include <Poco/Util/XMLConfiguration.h>
+#include <Parsers/ASTCreateQuery.h>
+#include <Parsers/ASTDropQuery.h>
+#include <Parsers/DumpASTNode.h>
+#include <Parsers/ParserCreateQuery.h>
+#include <Parsers/ParserDictionary.h>
+#include <Parsers/ParserDropQuery.h>
+#include <Parsers/ParserTablePropertiesQuery.h>
+#include <Parsers/TablePropertiesQueriesASTs.h>
+#include <Parsers/formatAST.h>
+#include <Parsers/parseQuery.h>
+#include <Dictionaries/getDictionaryConfigurationFromAST.h>
+#include <Dictionaries/registerDictionaries.h>
+
+#include <gtest/gtest.h>
+
+using namespace DB;
+
+static bool registered = false;
+/// For debug
+std::string configurationToString(const DictionaryConfigurationPtr & config)
+{
+    const Poco::Util::XMLConfiguration * xml_config = dynamic_cast<const Poco::Util::XMLConfiguration *>(config.get());
+    std::ostringstream oss;
+    xml_config->save(oss);
+    return oss.str();
+}
+
+TEST(ConvertDictionaryAST, SimpleDictConfiguration)
+{
+    if (!registered)
+    {
+        registerDictionaries();
+        registered = true;
+    }
+
+    String input = " CREATE DICTIONARY test.dict1"
+                   " ("
+                   "    key_column UInt64 DEFAULT 0,"
+                   "    second_column UInt8 DEFAULT 1,"
+                   "    third_column UInt8 DEFAULT 2"
+                   " )"
+                   " PRIMARY KEY key_column"
+                   " SOURCE(CLICKHOUSE(HOST 'localhost' PORT 9000 USER 'default' PASSWORD '' DB 'test' TABLE 'table_for_dict'))"
+                   " LAYOUT(FLAT())"
+                   " LIFETIME(MIN 1 MAX 10)"
+                   " RANGE(MIN second_column MAX third_column)";
+
+    ParserCreateDictionaryQuery parser;
+    ASTPtr ast = parseQuery(parser, input.data(), input.data() + input.size(), "", 0);
+    ASTCreateQuery * create = ast->as<ASTCreateQuery>();
+    DictionaryConfigurationPtr config = getDictionaryConfigurationFromAST(*create);
+
+    /// name
+    EXPECT_EQ(config->getString("dictionary.name"), "test.dict1");
+
+    /// lifetime
+    EXPECT_EQ(config->getInt("dictionary.lifetime.min"), 1);
+    EXPECT_EQ(config->getInt("dictionary.lifetime.max"), 10);
+
+    /// range
+    EXPECT_EQ(config->getString("dictionary.structure.range_min"), "second_column");
+    EXPECT_EQ(config->getString("dictionary.structure.range_max"), "third_column");
+
+    /// source
+    EXPECT_EQ(config->getString("dictionary.source.clickhouse.host"), "localhost");
+    EXPECT_EQ(config->getInt("dictionary.source.clickhouse.port"), 9000);
+    EXPECT_EQ(config->getString("dictionary.source.clickhouse.user"), "default");
+    EXPECT_EQ(config->getString("dictionary.source.clickhouse.password"), "");
+    EXPECT_EQ(config->getString("dictionary.source.clickhouse.db"), "test");
+    EXPECT_EQ(config->getString("dictionary.source.clickhouse.table"), "table_for_dict");
+
+    /// attributes and key
+    Poco::Util::AbstractConfiguration::Keys keys;
+    config->keys("dictionary.structure", keys);
+
+    EXPECT_EQ(keys.size(), 5); /// + ranged keys
+    EXPECT_EQ(config->getString("dictionary.structure." + keys[0] + ".name"), "second_column");
+    EXPECT_EQ(config->getString("dictionary.structure." + keys[0] + ".type"), "UInt8");
+    EXPECT_EQ(config->getInt("dictionary.structure." + keys[0] + ".null_value"), 1);
+
+    EXPECT_EQ(config->getString("dictionary.structure." + keys[1] + ".name"), "third_column");
+    EXPECT_EQ(config->getString("dictionary.structure." + keys[1] + ".type"), "UInt8");
+    EXPECT_EQ(config->getInt("dictionary.structure." + keys[1] + ".null_value"), 2);
+
+    EXPECT_EQ(keys[2], "id");
+    EXPECT_EQ(config->getString("dictionary.structure." + keys[2] + ".name"), "key_column");
+
+    /// layout
+    EXPECT_TRUE(config->has("dictionary.layout.flat"));
+}
+
+
+TEST(ConvertDictionaryAST, TrickyAttributes)
+{
+    if (!registered)
+    {
+        registerDictionaries();
+        registered = true;
+    }
+
+    String input = " CREATE DICTIONARY dict2"
+                   " ("
+                   "    key_column UInt64 IS_OBJECT_ID,"
+                   "    second_column UInt8 HIERARCHICAL INJECTIVE,"
+                   "    third_column UInt8 DEFAULT 2 EXPRESSION rand() % 100 * 77"
+                   " )"
+                   " PRIMARY KEY key_column"
+                   " LAYOUT(hashed())"
+                   " LIFETIME(MIN 1 MAX 10)"
+                   " SOURCE(CLICKHOUSE(HOST 'localhost'))";
+
+    ParserCreateDictionaryQuery parser;
+    ASTPtr ast = parseQuery(parser, input.data(), input.data() + input.size(), "", 0);
+    ASTCreateQuery * create = ast->as<ASTCreateQuery>();
+    DictionaryConfigurationPtr config = getDictionaryConfigurationFromAST(*create);
+
+    Poco::Util::AbstractConfiguration::Keys keys;
+    config->keys("dictionary.structure", keys);
+
+    EXPECT_EQ(keys.size(), 3);
+    EXPECT_EQ(config->getString("dictionary.structure." + keys[0] + ".name"), "second_column");
+    EXPECT_EQ(config->getString("dictionary.structure." + keys[0] + ".type"), "UInt8");
+    EXPECT_EQ(config->getString("dictionary.structure." + keys[0] + ".null_value"), "");
+    EXPECT_EQ(config->getString("dictionary.structure." + keys[0] + ".hierarchical"), "true");
+    EXPECT_EQ(config->getString("dictionary.structure." + keys[0] + ".injective"), "true");
+
+    EXPECT_EQ(config->getString("dictionary.structure." + keys[1] + ".name"), "third_column");
+    EXPECT_EQ(config->getString("dictionary.structure." + keys[1] + ".type"), "UInt8");
+    EXPECT_EQ(config->getInt("dictionary.structure." + keys[1] + ".null_value"), 2);
+    EXPECT_EQ(config->getString("dictionary.structure." + keys[1] + ".expression"), "(rand() % 100) * 77");
+
+    EXPECT_EQ(keys[2], "id");
+    EXPECT_EQ(config->getString("dictionary.structure." + keys[2] + ".name"), "key_column");
+}
+
+
+TEST(ConvertDictionaryAST, ComplexKeyAndLayoutWithParams)
+{
+    if (!registered)
+    {
+        registerDictionaries();
+        registered = true;
+    }
+
+    String input = " CREATE DICTIONARY dict4"
+                   " ("
+                   "    key_column1 String,"
+                   "    key_column2 UInt64,"
+                   "    third_column UInt8,"
+                   "    fourth_column UInt8"
+                   " )"
+                   " PRIMARY KEY key_column1, key_column2"
+                   " SOURCE(MYSQL())"
+                   " LAYOUT(COMPLEX_KEY_CACHE(size_in_cells 50))"
+                   " LIFETIME(MIN 1 MAX 10)";
+
+    ParserCreateDictionaryQuery parser;
+    ASTPtr ast = parseQuery(parser, input.data(), input.data() + input.size(), "", 0);
+    ASTCreateQuery * create = ast->as<ASTCreateQuery>();
+    DictionaryConfigurationPtr config = getDictionaryConfigurationFromAST(*create);
+
+    Poco::Util::AbstractConfiguration::Keys keys;
+    config->keys("dictionary.structure.key", keys);
+
+    EXPECT_EQ(keys.size(), 2);
+    EXPECT_EQ(config->getString("dictionary.structure.key." + keys[0] + ".name"), "key_column1");
+    EXPECT_EQ(config->getString("dictionary.structure.key." + keys[0] + ".type"), "String");
+
+    EXPECT_EQ(config->getString("dictionary.structure.key." + keys[1] + ".name"), "key_column2");
+    EXPECT_EQ(config->getString("dictionary.structure.key." + keys[1] + ".type"), "UInt64");
+
+    Poco::Util::AbstractConfiguration::Keys attrs;
+    config->keys("dictionary.structure", attrs);
+
+    EXPECT_EQ(attrs.size(), 3);
+    EXPECT_EQ(config->getString("dictionary.structure." + attrs[0] + ".name"), "third_column");
+    EXPECT_EQ(config->getString("dictionary.structure." + attrs[0] + ".type"), "UInt8");
+
+    EXPECT_EQ(config->getString("dictionary.structure." + attrs[1] + ".name"), "fourth_column");
+    EXPECT_EQ(config->getString("dictionary.structure." + attrs[1] + ".type"), "UInt8");
+
+    EXPECT_EQ(attrs[2], "key");
+
+    EXPECT_EQ(config->getInt("dictionary.layout.complex_key_cache.size_in_cells"), 50);
+}
+
+
+TEST(ConvertDictionaryAST, ComplexSource)
+{
+    if (!registered)
+    {
+        registerDictionaries();
+        registered = true;
+    }
+
+    String input = " CREATE DICTIONARY dict4"
+                   " ("
+                   "    key_column UInt64,"
+                   "    second_column UInt8,"
+                   "    third_column UInt8"
+                   " )"
+                   " PRIMARY KEY key_column"
+                   " SOURCE(MYSQL(HOST 'localhost' PORT 9000 USER 'default' REPLICA(HOST '127.0.0.1' PRIORITY 1) PASSWORD ''))"
+                   " LAYOUT(CACHE(size_in_cells 50))"
+                   " LIFETIME(MIN 1 MAX 10)"
+                   " RANGE(MIN second_column MAX third_column)";
+
+    ParserCreateDictionaryQuery parser;
+    ASTPtr ast = parseQuery(parser, input.data(), input.data() + input.size(), "", 0);
+    ASTCreateQuery * create = ast->as<ASTCreateQuery>();
+    DictionaryConfigurationPtr config = getDictionaryConfigurationFromAST(*create);
+    /// source
+    EXPECT_EQ(config->getString("dictionary.source.mysql.host"), "localhost");
+    EXPECT_EQ(config->getInt("dictionary.source.mysql.port"), 9000);
+    EXPECT_EQ(config->getString("dictionary.source.mysql.user"), "default");
+    EXPECT_EQ(config->getString("dictionary.source.mysql.password"), "");
+    EXPECT_EQ(config->getString("dictionary.source.mysql.replica.host"), "127.0.0.1");
+    EXPECT_EQ(config->getInt("dictionary.source.mysql.replica.priority"), 1);
+}

dbms/src/Functions/CRC.cpp

@@ -0,0 +1,146 @@
+#include <zlib.h>
+#include <DataTypes/DataTypeString.h>
+#include <Functions/FunctionFactory.h>
+#include <Functions/FunctionStringOrArrayToT.h>
+
+namespace
+{
+
+template <class T>
+struct CRCBase
+{
+    T tab[256];
+    CRCBase(T polynomial)
+    {
+        for (size_t i = 0; i < 256; ++i)
+        {
+            T c = i;
+            for (size_t j = 0; j < 8; ++j)
+            {
+                c = c & 1 ? polynomial ^ (c >> 1) : c >> 1;
+            }
+            tab[i] = c;
+        }
+    }
+};
+
+template <class T, T polynomial>
+struct CRCImpl
+{
+    using ReturnType = T;
+
+    static T make_crc(const unsigned char *buf, size_t size)
+    {
+        static CRCBase<ReturnType> base(polynomial);
+
+        T i, crc;
+
+        crc = 0;
+        for (i = 0; i < size; i++)
+        {
+            crc = base.tab[(crc ^ buf[i]) & 0xff] ^ (crc >> 8);
+        }
+        return crc;
+    }
+};
+
+static constexpr UInt64 CRC64_ECMA = 0xc96c5795d7870f42ULL;
+struct CRC64ECMAImpl : public CRCImpl<UInt64, CRC64_ECMA>
+{
+    static constexpr auto name = "CRC64";
+};
+
+static constexpr UInt32 CRC32_IEEE = 0xedb88320;
+struct CRC32IEEEImpl : public CRCImpl<UInt32, CRC32_IEEE>
+{
+    static constexpr auto name = "CRC32IEEE";
+};
+
+struct CRC32ZLIBImpl
+{
+    using ReturnType = UInt32;
+    static constexpr auto name = "CRC32";
+
+    static UInt32 make_crc(const unsigned char *buf, size_t size)
+    { return crc32_z(0L, buf, size); }
+};
+
+} // \anonymous
+
+namespace DB
+{
+
+namespace ErrorCodes
+{
+    extern const int ILLEGAL_TYPE_OF_ARGUMENT;
+}
+
+template <class Impl>
+struct CRCFunctionWrapper
+{
+    static constexpr auto is_fixed_to_constant = true;
+    using ReturnType = typename Impl::ReturnType;
+
+    static void vector(const ColumnString::Chars & data, const ColumnString::Offsets & offsets, PaddedPODArray<ReturnType> & res)
+    {
+        size_t size = offsets.size();
+
+        ColumnString::Offset prev_offset = 0;
+        for (size_t i = 0; i < size; ++i)
+        {
+            res[i] = do_crc(data, prev_offset, offsets[i] - prev_offset - 1);
+            prev_offset = offsets[i];
+        }
+    }
+
+    static void vector_fixed_to_constant(const ColumnString::Chars & data, size_t n, ReturnType & res) { res = do_crc(data, 0, n); }
+
+    static void vector_fixed_to_vector(const ColumnString::Chars & data, size_t n, PaddedPODArray<ReturnType> & res)
+    {
+        size_t size = data.size() / n;
+
+        for (size_t i = 0; i < size; ++i)
+        {
+            res[i] = do_crc(data, i * n, n);
+        }
+    }
+
+    [[noreturn]] static void array(const ColumnString::Offsets & /*offsets*/, PaddedPODArray<ReturnType> & /*res*/)
+    {
+        throw Exception("Cannot apply function " + std::string(Impl::name) + " to Array argument", ErrorCodes::ILLEGAL_TYPE_OF_ARGUMENT);
+    }
+
+private:
+    static ReturnType do_crc(const ColumnString::Chars & buf, size_t offset, size_t size)
+    {
+        const unsigned char * p = reinterpret_cast<const unsigned char *>(&buf[0]) + offset;
+        return Impl::make_crc(p, size);
+    }
+};
+
+template <class T>
+using FunctionCRC = FunctionStringOrArrayToT<CRCFunctionWrapper<T>, T, typename T::ReturnType>;
+// The same as IEEE variant, but uses 0xffffffff as initial value
+// This is the default
+//
+// (And zlib is used here, since it has optimized version)
+using FunctionCRC32ZLIB = FunctionCRC<CRC32ZLIBImpl>;
+// Uses CRC-32-IEEE 802.3 polynomial
+using FunctionCRC32IEEE = FunctionCRC<CRC32IEEEImpl>;
+// Uses CRC-64-ECMA polynomial
+using FunctionCRC64ECMA = FunctionCRC<CRC64ECMAImpl>;
+
+template <class T>
+void registerFunctionCRCImpl(FunctionFactory & factory)
+{
+    factory.registerFunction<T>(T::name, FunctionFactory::CaseInsensitive);
+}
+
+void registerFunctionCRC(FunctionFactory & factory)
+{
+    registerFunctionCRCImpl<FunctionCRC32ZLIB>(factory);
+    registerFunctionCRCImpl<FunctionCRC32IEEE>(factory);
+    registerFunctionCRCImpl<FunctionCRC64ECMA>(factory);
+}
+
+}

dbms/src/Functions/CRC32.cpp

@@ -1,68 +0,0 @@
-#include <zlib.h>
-#include <DataTypes/DataTypeString.h>
-#include <Functions/FunctionFactory.h>
-#include <Functions/FunctionStringOrArrayToT.h>
-
-
-namespace DB
-{
-namespace ErrorCodes
-{
-    extern const int ILLEGAL_TYPE_OF_ARGUMENT;
-}
-
-/** Calculates the CRC32 of a string
-  */
-struct CRC32Impl
-{
-    static constexpr auto is_fixed_to_constant = true;
-
-    static void vector(const ColumnString::Chars & data, const ColumnString::Offsets & offsets, PaddedPODArray<UInt32> & res)
-    {
-        size_t size = offsets.size();
-
-        ColumnString::Offset prev_offset = 0;
-        for (size_t i = 0; i < size; ++i)
-        {
-            res[i] = do_crc32(data, prev_offset, offsets[i] - prev_offset - 1);
-            prev_offset = offsets[i];
-        }
-    }
-
-    static void vector_fixed_to_constant(const ColumnString::Chars & data, size_t n, UInt32 & res) { res = do_crc32(data, 0, n); }
-
-    static void vector_fixed_to_vector(const ColumnString::Chars & data, size_t n, PaddedPODArray<UInt32> & res)
-    {
-        size_t size = data.size() / n;
-
-        for (size_t i = 0; i < size; ++i)
-        {
-            res[i] = do_crc32(data, i * n, n);
-        }
-    }
-
-    [[noreturn]] static void array(const ColumnString::Offsets & /*offsets*/, PaddedPODArray<UInt32> & /*res*/)
-    {
-        throw Exception("Cannot apply function CRC32 to Array argument", ErrorCodes::ILLEGAL_TYPE_OF_ARGUMENT);
-    }
-
-private:
-    static uint32_t do_crc32(const ColumnString::Chars & buf, size_t offset, size_t size)
-    {
-        const unsigned char * p = reinterpret_cast<const unsigned char *>(&buf[0]) + offset;
-        return crc32(0L, p, size);
-    }
-};
-
-struct NameCRC32
-{
-    static constexpr auto name = "CRC32";
-};
-using FunctionCRC32 = FunctionStringOrArrayToT<CRC32Impl, NameCRC32, UInt32>;
-
-void registerFunctionCRC32(FunctionFactory & factory)
-{
-    factory.registerFunction<FunctionCRC32>(NameCRC32::name, FunctionFactory::CaseInsensitive);
-}
-
-}

dbms/src/Functions/FunctionsJSON.cpp

@@ -8,6 +8,7 @@ namespace DB
 void registerFunctionsJSON(FunctionFactory & factory)
 {
     factory.registerFunction<FunctionJSON<NameJSONHas, JSONHasImpl>>();
+    factory.registerFunction<FunctionJSON<NameIsValidJSON, IsValidJSONImpl>>();
     factory.registerFunction<FunctionJSON<NameJSONLength, JSONLengthImpl>>();
     factory.registerFunction<FunctionJSON<NameJSONKey, JSONKeyImpl>>();
     factory.registerFunction<FunctionJSON<NameJSONType, JSONTypeImpl>>();

dbms/src/Functions/FunctionsJSON.h

@@ -279,6 +279,7 @@ private:
 
 
 struct NameJSONHas { static constexpr auto name{"JSONHas"}; };
+struct NameIsValidJSON { static constexpr auto name{"isValidJSON"}; };
 struct NameJSONLength { static constexpr auto name{"JSONLength"}; };
 struct NameJSONKey { static constexpr auto name{"JSONKey"}; };
 struct NameJSONType { static constexpr auto name{"JSONType"}; };
@@ -311,6 +312,36 @@ public:
 };
 
 
+template <typename JSONParser>
+class IsValidJSONImpl
+{
+public:
+    static DataTypePtr getType(const char * function_name, const ColumnsWithTypeAndName & arguments)
+    {
+        if (arguments.size() != 1)
+        {
+            /// IsValidJSON() shouldn't get parameters other than JSON.
+            throw Exception{"Function " + String(function_name) + " needs exactly one argument",
+                            ErrorCodes::NUMBER_OF_ARGUMENTS_DOESNT_MATCH};
+        }
+        return std::make_shared<DataTypeUInt8>();
+    }
+
+    using Iterator = typename JSONParser::Iterator;
+    static bool addValueToColumn(IColumn & dest, const Iterator &)
+    {
+        /// This function is called only if JSON is valid.
+        /// If JSON isn't valid then `FunctionJSON::Executor::run()` adds default value (=zero) to `dest` without calling this function.
+        ColumnVector<UInt8> & col_vec = assert_cast<ColumnVector<UInt8> &>(dest);
+        col_vec.insertValue(1);
+        return true;
+    }
+
+    static constexpr size_t num_extra_arguments = 0;
+    static void prepare(const char *, const Block &, const ColumnNumbers &, size_t) {}
+};
+
+
 template <typename JSONParser>
 class JSONLengthImpl
 {

dbms/src/Functions/getScalar.cpp

@@ -0,0 +1,68 @@
+#include <Functions/IFunction.h>
+#include <Functions/FunctionFactory.h>
+#include <Functions/FunctionHelpers.h>
+#include <DataTypes/DataTypeString.h>
+#include <Columns/ColumnString.h>
+#include <Interpreters/Context.h>
+#include <Common/Macros.h>
+#include <Core/Field.h>
+
+
+namespace DB
+{
+
+namespace ErrorCodes
+{
+    extern const int ILLEGAL_TYPE_OF_ARGUMENT;
+    extern const int ILLEGAL_COLUMN;
+}
+
+/** Get scalar value of sub queries from query context via IAST::Hash.
+  */
+class FunctionGetScalar : public IFunction
+{
+public:
+    static constexpr auto name = "__getScalar";
+    static FunctionPtr create(const Context & context)
+    {
+        return std::make_shared<FunctionGetScalar>(context);
+    }
+
+    FunctionGetScalar(const Context & context_) : context(context_) {}
+
+    String getName() const override
+    {
+        return name;
+    }
+
+    size_t getNumberOfArguments() const override
+    {
+        return 1;
+    }
+
+    DataTypePtr getReturnTypeImpl(const ColumnsWithTypeAndName & arguments) const override
+    {
+        if (arguments.size() != 1 || !isString(arguments[0].type) || !isColumnConst(*arguments[0].column))
+            throw Exception("Function " + getName() + " accepts one const string argument", ErrorCodes::ILLEGAL_TYPE_OF_ARGUMENT);
+        auto scalar_name = assert_cast<const ColumnConst &>(*arguments[0].column).getField().get<String>();
+        scalar = context.getScalar(scalar_name).getByPosition(0);
+        return scalar.type;
+    }
+
+    void executeImpl(Block & block, const ColumnNumbers &, size_t result, size_t input_rows_count) override
+    {
+        block.getByPosition(result).column = ColumnConst::create(scalar.column, input_rows_count);
+    }
+
+private:
+    mutable ColumnWithTypeAndName scalar;
+    const Context & context;
+};
+
+
+void registerFunctionGetScalar(FunctionFactory & factory)
+{
+    factory.registerFunction<FunctionGetScalar>();
+}
+
+}

dbms/src/Functions/registerFunctionsMiscellaneous.cpp

@@ -52,6 +52,7 @@ void registerFunctionEvalMLMethod(FunctionFactory &);
 void registerFunctionBasename(FunctionFactory &);
 void registerFunctionTransform(FunctionFactory &);
 void registerFunctionGetMacro(FunctionFactory &);
+void registerFunctionGetScalar(FunctionFactory &);
 
 #if USE_ICU
 void registerFunctionConvertCharset(FunctionFactory &);
@@ -106,6 +107,7 @@ void registerFunctionsMiscellaneous(FunctionFactory & factory)
     registerFunctionBasename(factory);
     registerFunctionTransform(factory);
     registerFunctionGetMacro(factory);
+    registerFunctionGetScalar(factory);
 
 #if USE_ICU
     registerFunctionConvertCharset(factory);

dbms/src/Functions/registerFunctionsString.cpp

@@ -20,7 +20,7 @@ void registerFunctionReverseUTF8(FunctionFactory &);
 void registerFunctionsConcat(FunctionFactory &);
 void registerFunctionFormat(FunctionFactory &);
 void registerFunctionSubstring(FunctionFactory &);
-void registerFunctionCRC32(FunctionFactory &);
+void registerFunctionCRC(FunctionFactory &);
 void registerFunctionAppendTrailingCharIfAbsent(FunctionFactory &);
 void registerFunctionStartsWith(FunctionFactory &);
 void registerFunctionEndsWith(FunctionFactory &);
@@ -47,7 +47,7 @@ void registerFunctionsString(FunctionFactory & factory)
     registerFunctionLowerUTF8(factory);
     registerFunctionUpperUTF8(factory);
     registerFunctionReverse(factory);
-    registerFunctionCRC32(factory);
+    registerFunctionCRC(factory);
     registerFunctionReverseUTF8(factory);
     registerFunctionsConcat(factory);
     registerFunctionFormat(factory);

dbms/src/Interpreters/ActionLocksManager.cpp

@@ -23,7 +23,7 @@ template <typename F>
 inline void forEachTable(Context & context, F && f)
 {
     for (auto & elem : context.getDatabases())
-        for (auto iterator = elem.second->getIterator(context); iterator->isValid(); iterator->next())
+        for (auto iterator = elem.second->getTablesIterator(context); iterator->isValid(); iterator->next())
             f(iterator->table());
 
 }

dbms/src/Interpreters/ActionsVisitor.cpp

@@ -29,7 +29,7 @@
 #include <Parsers/ASTTablesInSelectQuery.h>
 
 #include <Interpreters/ExpressionActions.h>
-#include <Interpreters/QueryNormalizer.h>
+#include <Interpreters/misc.h>
 #include <Interpreters/ActionsVisitor.h>
 #include <Interpreters/InterpreterSelectWithUnionQuery.h>
 #include <Interpreters/Set.h>

dbms/src/Interpreters/Aggregator.h

@@ -11,6 +11,9 @@
 #include <Common/HashTable/FixedHashMap.h>
 #include <Common/HashTable/HashMap.h>
 #include <Common/HashTable/TwoLevelHashMap.h>
+#include <Common/HashTable/StringHashMap.h>
+#include <Common/HashTable/TwoLevelStringHashMap.h>
+
 #include <Common/ThreadPool.h>
 #include <Common/UInt128.h>
 #include <Common/LRUCache.h>
@@ -69,12 +72,20 @@ using AggregatedDataWithUInt8Key = FixedHashMap<UInt8, AggregateDataPtr>;
 using AggregatedDataWithUInt16Key = FixedHashMap<UInt16, AggregateDataPtr>;
 
 using AggregatedDataWithUInt64Key = HashMap<UInt64, AggregateDataPtr, HashCRC32<UInt64>>;
+
+using AggregatedDataWithShortStringKey = StringHashMap<AggregateDataPtr>;
+
 using AggregatedDataWithStringKey = HashMapWithSavedHash<StringRef, AggregateDataPtr>;
+
 using AggregatedDataWithKeys128 = HashMap<UInt128, AggregateDataPtr, UInt128HashCRC32>;
 using AggregatedDataWithKeys256 = HashMap<UInt256, AggregateDataPtr, UInt256HashCRC32>;
 
 using AggregatedDataWithUInt64KeyTwoLevel = TwoLevelHashMap<UInt64, AggregateDataPtr, HashCRC32<UInt64>>;
+
+using AggregatedDataWithShortStringKeyTwoLevel = TwoLevelStringHashMap<AggregateDataPtr>;
+
 using AggregatedDataWithStringKeyTwoLevel = TwoLevelHashMapWithSavedHash<StringRef, AggregateDataPtr>;
+
 using AggregatedDataWithKeys128TwoLevel = TwoLevelHashMap<UInt128, AggregateDataPtr, UInt128HashCRC32>;
 using AggregatedDataWithKeys256TwoLevel = TwoLevelHashMap<UInt256, AggregateDataPtr, UInt256HashCRC32>;
 
@@ -139,6 +150,8 @@ struct AggregationDataWithNullKeyTwoLevel : public Base
 
 template <typename ... Types>
 using HashTableWithNullKey = AggregationDataWithNullKey<HashMapTable<Types ...>>;
+template <typename ... Types>
+using StringHashTableWithNullKey = AggregationDataWithNullKey<StringHashMap<Types ...>>;
 
 using AggregatedDataWithNullableUInt8Key = AggregationDataWithNullKey<AggregatedDataWithUInt8Key>;
 using AggregatedDataWithNullableUInt16Key = AggregationDataWithNullKey<AggregatedDataWithUInt16Key>;
@@ -149,6 +162,10 @@ using AggregatedDataWithNullableStringKey = AggregationDataWithNullKey<Aggregate
 using AggregatedDataWithNullableUInt64KeyTwoLevel = AggregationDataWithNullKeyTwoLevel<
         TwoLevelHashMap<UInt64, AggregateDataPtr, HashCRC32<UInt64>,
         TwoLevelHashTableGrower<>, HashTableAllocator, HashTableWithNullKey>>;
+
+using AggregatedDataWithNullableShortStringKeyTwoLevel = AggregationDataWithNullKeyTwoLevel<
+        TwoLevelStringHashMap<AggregateDataPtr, HashTableAllocator, StringHashTableWithNullKey>>;
+
 using AggregatedDataWithNullableStringKeyTwoLevel = AggregationDataWithNullKeyTwoLevel<
         TwoLevelHashMapWithSavedHash<StringRef, AggregateDataPtr, DefaultHash<StringRef>,
         TwoLevelHashTableGrower<>, HashTableAllocator, HashTableWithNullKey>>;
@@ -216,6 +233,32 @@ struct AggregationMethodString
 };
 
 
+/// Same as above but without cache
+template <typename TData>
+struct AggregationMethodStringNoCache
+{
+    using Data = TData;
+    using Key = typename Data::key_type;
+    using Mapped = typename Data::mapped_type;
+
+    Data data;
+
+    AggregationMethodStringNoCache() {}
+
+    template <typename Other>
+    AggregationMethodStringNoCache(const Other & other) : data(other.data) {}
+
+    using State = ColumnsHashing::HashMethodString<typename Data::value_type, Mapped, true, false>;
+
+    static const bool low_cardinality_optimization = false;
+
+    static void insertKeyIntoColumns(const StringRef & key, MutableColumns & key_columns, const Sizes &)
+    {
+        key_columns[0]->insertData(key.data, key.size);
+    }
+};
+
+
 /// For the case where there is one fixed-length string key.
 template <typename TData>
 struct AggregationMethodFixedString
@@ -241,6 +284,32 @@ struct AggregationMethodFixedString
     }
 };
 
+/// Same as above but without cache
+template <typename TData>
+struct AggregationMethodFixedStringNoCache
+{
+    using Data = TData;
+    using Key = typename Data::key_type;
+    using Mapped = typename Data::mapped_type;
+
+    Data data;
+
+    AggregationMethodFixedStringNoCache() {}
+
+    template <typename Other>
+    AggregationMethodFixedStringNoCache(const Other & other) : data(other.data) {}
+
+    using State = ColumnsHashing::HashMethodFixedString<typename Data::value_type, Mapped, true, false>;
+
+    static const bool low_cardinality_optimization = false;
+
+    static void insertKeyIntoColumns(const StringRef & key, MutableColumns & key_columns, const Sizes &)
+    {
+        key_columns[0]->insertData(key.data, key.size);
+    }
+};
+
+
 /// Single low cardinality column.
 template <typename SingleColumnMethod>
 struct AggregationMethodSingleLowCardinalityColumn : public SingleColumnMethod
@@ -434,16 +503,16 @@ struct AggregatedDataVariants : private boost::noncopyable
 
     std::unique_ptr<AggregationMethodOneNumber<UInt32, AggregatedDataWithUInt64Key>>         key32;
     std::unique_ptr<AggregationMethodOneNumber<UInt64, AggregatedDataWithUInt64Key>>         key64;
-    std::unique_ptr<AggregationMethodString<AggregatedDataWithStringKey>>                    key_string;
-    std::unique_ptr<AggregationMethodFixedString<AggregatedDataWithStringKey>>               key_fixed_string;
+    std::unique_ptr<AggregationMethodStringNoCache<AggregatedDataWithShortStringKey>>               key_string;
+    std::unique_ptr<AggregationMethodFixedStringNoCache<AggregatedDataWithShortStringKey>>          key_fixed_string;
     std::unique_ptr<AggregationMethodKeysFixed<AggregatedDataWithKeys128>>                   keys128;
     std::unique_ptr<AggregationMethodKeysFixed<AggregatedDataWithKeys256>>                   keys256;
     std::unique_ptr<AggregationMethodSerialized<AggregatedDataWithStringKey>>                serialized;
 
     std::unique_ptr<AggregationMethodOneNumber<UInt32, AggregatedDataWithUInt64KeyTwoLevel>> key32_two_level;
     std::unique_ptr<AggregationMethodOneNumber<UInt64, AggregatedDataWithUInt64KeyTwoLevel>> key64_two_level;
-    std::unique_ptr<AggregationMethodString<AggregatedDataWithStringKeyTwoLevel>>            key_string_two_level;
-    std::unique_ptr<AggregationMethodFixedString<AggregatedDataWithStringKeyTwoLevel>>       key_fixed_string_two_level;
+    std::unique_ptr<AggregationMethodStringNoCache<AggregatedDataWithShortStringKeyTwoLevel>>       key_string_two_level;
+    std::unique_ptr<AggregationMethodFixedStringNoCache<AggregatedDataWithShortStringKeyTwoLevel>>  key_fixed_string_two_level;
     std::unique_ptr<AggregationMethodKeysFixed<AggregatedDataWithKeys128TwoLevel>>           keys128_two_level;
     std::unique_ptr<AggregationMethodKeysFixed<AggregatedDataWithKeys256TwoLevel>>           keys256_two_level;
     std::unique_ptr<AggregationMethodSerialized<AggregatedDataWithStringKeyTwoLevel>>        serialized_two_level;

dbms/src/Interpreters/AsynchronousMetrics.cpp

@@ -167,7 +167,7 @@ void AsynchronousMetrics::update()
             /// Lazy database can not contain MergeTree tables
             if (db.second->getEngineName() == "Lazy")
                 continue;
-            for (auto iterator = db.second->getIterator(context); iterator->isValid(); iterator->next())
+            for (auto iterator = db.second->getTablesIterator(context); iterator->isValid(); iterator->next())
             {
                 ++total_number_of_tables;
                 auto & table = iterator->table();

dbms/src/Interpreters/ClusterProxy/SelectStreamFactory.cpp

@@ -33,11 +33,13 @@ SelectStreamFactory::SelectStreamFactory(
     const Block & header_,
     QueryProcessingStage::Enum processed_stage_,
     QualifiedTableName main_table_,
+    const Scalars & scalars_,
     const Tables & external_tables_)
     : header(header_),
     processed_stage{processed_stage_},
     main_table(std::move(main_table_)),
     table_func_ptr{nullptr},
+    scalars{scalars_},
     external_tables{external_tables_}
 {
 }
@@ -46,10 +48,12 @@ SelectStreamFactory::SelectStreamFactory(
     const Block & header_,
     QueryProcessingStage::Enum processed_stage_,
     ASTPtr table_func_ptr_,
+    const Scalars & scalars_,
     const Tables & external_tables_)
     : header(header_),
     processed_stage{processed_stage_},
     table_func_ptr{table_func_ptr_},
+    scalars{scalars_},
     external_tables{external_tables_}
 {
 }
@@ -92,7 +96,8 @@ void SelectStreamFactory::createForShard(
 
     auto emplace_remote_stream = [&]()
     {
-        auto stream = std::make_shared<RemoteBlockInputStream>(shard_info.pool, query, header, context, nullptr, throttler, external_tables, processed_stage);
+        auto stream = std::make_shared<RemoteBlockInputStream>(
+            shard_info.pool, query, header, context, nullptr, throttler, scalars, external_tables, processed_stage);
         stream->setPoolMode(PoolMode::GET_MANY);
         if (!table_func_ptr)
             stream->setMainTable(main_table);
@@ -190,8 +195,8 @@ void SelectStreamFactory::createForShard(
 
         auto lazily_create_stream = [
                 pool = shard_info.pool, shard_num = shard_info.shard_num, query, header = header, query_ast, context, throttler,
-                main_table = main_table, table_func_ptr = table_func_ptr, external_tables = external_tables, stage = processed_stage,
-                local_delay]()
+                main_table = main_table, table_func_ptr = table_func_ptr, scalars = scalars, external_tables = external_tables,
+                stage = processed_stage, local_delay]()
             -> BlockInputStreamPtr
         {
             auto current_settings = context.getSettingsRef();
@@ -233,7 +238,7 @@ void SelectStreamFactory::createForShard(
                     connections.emplace_back(std::move(try_result.entry));
 
                 return std::make_shared<RemoteBlockInputStream>(
-                    std::move(connections), query, header, context, nullptr, throttler, external_tables, stage);
+                    std::move(connections), query, header, context, nullptr, throttler, scalars, external_tables, stage);
             }
         };
 

dbms/src/Interpreters/ClusterProxy/SelectStreamFactory.h

@@ -18,6 +18,7 @@ public:
         const Block & header_,
         QueryProcessingStage::Enum processed_stage_,
         QualifiedTableName main_table_,
+        const Scalars & scalars_,
         const Tables & external_tables);
 
     /// TableFunction in a query.
@@ -25,6 +26,7 @@ public:
         const Block & header_,
         QueryProcessingStage::Enum processed_stage_,
         ASTPtr table_func_ptr_,
+        const Scalars & scalars_,
         const Tables & external_tables_);
 
     void createForShard(
@@ -38,6 +40,7 @@ private:
     QueryProcessingStage::Enum processed_stage;
     QualifiedTableName main_table;
     ASTPtr table_func_ptr;
+    Scalars scalars;
     Tables external_tables;
 };
 

dbms/src/Interpreters/CollectJoinOnKeysVisitor.cpp

@@ -164,7 +164,8 @@ size_t CollectJoinOnKeysMatcher::getTableForIdentifiers(std::vector<const ASTIde
 
         /// Column name could be cropped to a short form in TranslateQualifiedNamesVisitor.
         /// In this case it saves membership in IdentifierSemantic.
-        size_t membership = IdentifierSemantic::getMembership(*identifier);
+        auto opt = IdentifierSemantic::getMembership(*identifier);
+        size_t membership = opt ? (*opt + 1) : 0;
 
         if (!membership)
         {

dbms/src/Interpreters/Context.cpp

@@ -30,6 +30,7 @@
 #include <Dictionaries/Embedded/GeoDictionariesLoader.h>
 #include <Interpreters/EmbeddedDictionaries.h>
 #include <Interpreters/ExternalLoaderXMLConfigRepository.h>
+#include <Interpreters/ExternalLoaderDatabaseConfigRepository.h>
 #include <Interpreters/ExternalDictionariesLoader.h>
 #include <Interpreters/ExternalModelsLoader.h>
 #include <Interpreters/ExpressionActions.h>
@@ -88,6 +89,8 @@ namespace ErrorCodes
     extern const int SESSION_IS_LOCKED;
     extern const int CANNOT_GET_CREATE_TABLE_QUERY;
     extern const int LOGICAL_ERROR;
+    extern const int SCALAR_ALREADY_EXISTS;
+    extern const int UNKNOWN_SCALAR;
 }
 
 
@@ -192,7 +195,7 @@ struct ContextShared
     bool shutdown_called = false;
 
     /// Do not allow simultaneous execution of DDL requests on the same table.
-    /// database -> table -> (mutex, counter), counter: how many threads are running a query on the table at the same time
+    /// database -> object -> (mutex, counter), counter: how many threads are running a query on the table at the same time
     /// For the duration of the operation, an element is placed here, and an object is returned,
     /// which deletes the element in the destructor when counter becomes zero.
     /// In case the element already exists, waits, when query will be executed in other thread. See class DDLGuard below.
@@ -793,6 +796,16 @@ bool Context::isTableExist(const String & database_name, const String & table_na
         && it->second->isTableExist(*this, table_name);
 }
 
+bool Context::isDictionaryExists(const String & database_name, const String & dictionary_name) const
+{
+    auto lock = getLock();
+
+    String db = resolveDatabase(database_name, current_database);
+    checkDatabaseAccessRightsImpl(db);
+
+    Databases::const_iterator it = shared->databases.find(db);
+    return shared->databases.end() != it && it->second->isDictionaryExist(*this, dictionary_name);
+}
 
 bool Context::isDatabaseExist(const String & database_name) const
 {
@@ -808,22 +821,6 @@ bool Context::isExternalTableExist(const String & table_name) const
 }
 
 
-void Context::assertTableExists(const String & database_name, const String & table_name) const
-{
-    auto lock = getLock();
-
-    String db = resolveDatabase(database_name, current_database);
-    checkDatabaseAccessRightsImpl(db);
-
-    Databases::const_iterator it = shared->databases.find(db);
-    if (shared->databases.end() == it)
-        throw Exception("Database " + backQuoteIfNeed(db) + " doesn't exist", ErrorCodes::UNKNOWN_DATABASE);
-
-    if (!it->second->isTableExist(*this, table_name))
-        throw Exception("Table " + backQuoteIfNeed(db) + "." + backQuoteIfNeed(table_name) + " doesn't exist.", ErrorCodes::UNKNOWN_TABLE);
-}
-
-
 void Context::assertTableDoesntExist(const String & database_name, const String & table_name, bool check_database_access_rights) const
 {
     auto lock = getLock();
@@ -863,6 +860,21 @@ void Context::assertDatabaseDoesntExist(const String & database_name) const
 }
 
 
+const Scalars & Context::getScalars() const
+{
+    return scalars;
+}
+
+
+const Block & Context::getScalar(const String & name) const
+{
+    auto it = scalars.find(name);
+    if (scalars.end() == it)
+        throw Exception("Scalar " + backQuoteIfNeed(name) + " doesn't exist (internal bug)", ErrorCodes::UNKNOWN_SCALAR);
+    return it->second;
+}
+
+
 Tables Context::getExternalTables() const
 {
     auto lock = getLock();
@@ -960,6 +972,19 @@ void Context::addExternalTable(const String & table_name, const StoragePtr & sto
     external_tables[table_name] = std::pair(storage, ast);
 }
 
+
+void Context::addScalar(const String & name, const Block & block)
+{
+    scalars[name] = block;
+}
+
+
+bool Context::hasScalar(const String & name) const
+{
+    return scalars.count(name);
+}
+
+
 StoragePtr Context::tryRemoveExternalTable(const String & table_name)
 {
     TableAndCreateASTs::const_iterator it = external_tables.find(table_name);
@@ -1047,9 +1072,10 @@ void Context::addDatabase(const String & database_name, const DatabasePtr & data
 DatabasePtr Context::detachDatabase(const String & database_name)
 {
     auto lock = getLock();
-
     auto res = getDatabase(database_name);
+    getExternalDictionariesLoader().removeConfigRepository(database_name);
     shared->databases.erase(database_name);
+
     return res;
 }
 
@@ -1064,6 +1090,17 @@ ASTPtr Context::getCreateTableQuery(const String & database_name, const String &
     return shared->databases[db]->getCreateTableQuery(*this, table_name);
 }
 
+
+ASTPtr Context::getCreateDictionaryQuery(const String & database_name, const String & dictionary_name) const
+{
+    auto lock = getLock();
+
+    String db = resolveDatabase(database_name, current_database);
+    assertDatabaseExists(db);
+
+    return shared->databases[db]->getCreateDictionaryQuery(*this, dictionary_name);
+}
+
 ASTPtr Context::getCreateExternalTableQuery(const String & table_name) const
 {
     TableAndCreateASTs::const_iterator jt = external_tables.find(table_name);
@@ -1309,21 +1346,13 @@ EmbeddedDictionaries & Context::getEmbeddedDictionaries()
 
 const ExternalDictionariesLoader & Context::getExternalDictionariesLoader() const
 {
-    {
-        std::lock_guard lock(shared->external_dictionaries_mutex);
-        if (shared->external_dictionaries_loader)
-            return *shared->external_dictionaries_loader;
-    }
-
-    const auto & config = getConfigRef();
     std::lock_guard lock(shared->external_dictionaries_mutex);
     if (!shared->external_dictionaries_loader)
     {
         if (!this->global_context)
             throw Exception("Logical error: there is no global context", ErrorCodes::LOGICAL_ERROR);
 
-        auto config_repository = std::make_unique<ExternalLoaderXMLConfigRepository>(config, "dictionaries_config");
-        shared->external_dictionaries_loader.emplace(std::move(config_repository), *this->global_context);
+        shared->external_dictionaries_loader.emplace(*this->global_context);
     }
     return *shared->external_dictionaries_loader;
 }
@@ -1342,8 +1371,7 @@ const ExternalModelsLoader & Context::getExternalModelsLoader() const
         if (!this->global_context)
             throw Exception("Logical error: there is no global context", ErrorCodes::LOGICAL_ERROR);
 
-        auto config_repository = std::make_unique<ExternalLoaderXMLConfigRepository>(getConfigRef(), "models_config");
-        shared->external_models_loader.emplace(std::move(config_repository), *this->global_context);
+        shared->external_models_loader.emplace(*this->global_context);
     }
     return *shared->external_models_loader;
 }
@@ -2050,7 +2078,7 @@ void Context::dropCompiledExpressionCache() const
 #endif
 
 
-void Context::addXDBCBridgeCommand(std::unique_ptr<ShellCommand> cmd)
+void Context::addXDBCBridgeCommand(std::unique_ptr<ShellCommand> cmd) const
 {
     auto lock = getLock();
     shared->bridge_commands.emplace_back(std::move(cmd));

dbms/src/Interpreters/Context.h

@@ -107,6 +107,9 @@ using InputInitializer = std::function<void(Context &, const StoragePtr &)>;
 /// Callback for reading blocks of data from client for function input()
 using InputBlocksReader = std::function<Block(Context &)>;
 
+/// Scalar results of sub queries
+using Scalars = std::map<String, Block>;
+
 /// An empty interface for an arbitrary object that may be attached by a shared pointer
 /// to query context, when using ClickHouse as a library.
 struct IHostContext
@@ -146,6 +149,7 @@ private:
     String default_format;  /// Format, used when server formats data by itself and if query does not have FORMAT specification.
                             /// Thus, used in HTTP interface. If not specified - then some globally default format is used.
     TableAndCreateASTs external_tables;     /// Temporary tables.
+    Scalars scalars;
     StoragePtr view_source;                 /// Temporary StorageValues used to generate alias columns for materialized views
     Tables table_function_results;          /// Temporary tables obtained by execution of table functions. Keyed by AST tree id.
     Context * query_context = nullptr;
@@ -250,9 +254,9 @@ public:
     /// Checking the existence of the table/database. Database can be empty - in this case the current database is used.
     bool isTableExist(const String & database_name, const String & table_name) const;
     bool isDatabaseExist(const String & database_name) const;
+    bool isDictionaryExists(const String & database_name, const String & dictionary_name) const;
     bool isExternalTableExist(const String & table_name) const;
     bool hasDatabaseAccessRights(const String & database_name) const;
-    void assertTableExists(const String & database_name, const String & table_name) const;
 
     bool hasDictionaryAccessRights(const String & dictionary_name) const;
 
@@ -266,11 +270,15 @@ public:
     void assertDatabaseDoesntExist(const String & database_name) const;
     void checkDatabaseAccessRights(const std::string & database_name) const;
 
+    const Scalars & getScalars() const;
+    const Block & getScalar(const String & name) const;
     Tables getExternalTables() const;
     StoragePtr tryGetExternalTable(const String & table_name) const;
     StoragePtr getTable(const String & database_name, const String & table_name) const;
     StoragePtr tryGetTable(const String & database_name, const String & table_name) const;
     void addExternalTable(const String & table_name, const StoragePtr & storage, const ASTPtr & ast = {});
+    void addScalar(const String & name, const Block & block);
+    bool hasScalar(const String & name) const;
     StoragePtr tryRemoveExternalTable(const String & table_name);
 
     StoragePtr executeTableFunction(const ASTPtr & table_expression);
@@ -361,6 +369,7 @@ public:
     ASTPtr getCreateTableQuery(const String & database_name, const String & table_name) const;
     ASTPtr getCreateExternalTableQuery(const String & table_name) const;
     ASTPtr getCreateDatabaseQuery(const String & database_name) const;
+    ASTPtr getCreateDictionaryQuery(const String & database_name, const String & dictionary_name) const;
 
     const DatabasePtr getDatabase(const String & database_name) const;
     DatabasePtr getDatabase(const String & database_name);
@@ -550,7 +559,7 @@ public:
 #endif
 
     /// Add started bridge command. It will be killed after context destruction
-    void addXDBCBridgeCommand(std::unique_ptr<ShellCommand> cmd);
+    void addXDBCBridgeCommand(std::unique_ptr<ShellCommand> cmd) const;
 
     IHostContextPtr & getHostContext();
     const IHostContextPtr & getHostContext() const;

dbms/src/Interpreters/CrossToInnerJoinVisitor.cpp

@@ -4,7 +4,7 @@
 #include <Interpreters/CrossToInnerJoinVisitor.h>
 #include <Interpreters/DatabaseAndTableWithAlias.h>
 #include <Interpreters/IdentifierSemantic.h>
-#include <Interpreters/QueryNormalizer.h> // for functionIsInOperator
+#include <Interpreters/misc.h>
 #include <Parsers/ASTSelectQuery.h>
 #include <Parsers/ASTTablesInSelectQuery.h>
 #include <Parsers/ASTIdentifier.h>
@@ -90,11 +90,14 @@ public:
     using TypeToVisit = const ASTFunction;
 
     CheckExpressionVisitorData(const std::vector<JoinedTable> & tables_)
-        : tables(tables_)
+        : joined_tables(tables_)
         , ands_only(true)
-    {}
+    {
+        for (auto & joined : joined_tables)
+            tables.push_back(joined.table);
+    }
 
-    void visit(const ASTFunction & node, ASTPtr & ast)
+    void visit(const ASTFunction & node, const ASTPtr & ast)
     {
         if (!ands_only)
             return;
@@ -156,7 +159,8 @@ public:
     }
 
 private:
-    const std::vector<JoinedTable> & tables;
+    const std::vector<JoinedTable> & joined_tables;
+    std::vector<DatabaseAndTableWithAlias> tables;
     std::map<size_t, std::vector<ASTPtr>> asts_to_join_on;
     bool ands_only;
 
@@ -180,31 +184,16 @@ private:
     /// @return table position to attach expression to or 0.
     size_t checkIdentifiers(const ASTIdentifier & left, const ASTIdentifier & right)
     {
-        /// {best_match, best_table_pos}
-        std::pair<size_t, size_t> left_best{0, 0};
-        std::pair<size_t, size_t> right_best{0, 0};
+        size_t left_table_pos = 0;
+        bool left_match = IdentifierSemantic::chooseTable(left, tables, left_table_pos);
 
-        for (size_t i = 0; i < tables.size(); ++i)
+        size_t right_table_pos = 0;
+        bool right_match = IdentifierSemantic::chooseTable(right, tables, right_table_pos);
+
+        if (left_match && right_match && (left_table_pos != right_table_pos))
         {
-            size_t match = IdentifierSemantic::canReferColumnToTable(left, tables[i].table);
-            if (match > left_best.first)
-            {
-                left_best.first = match;
-                left_best.second = i;
-            }
-
-            match = IdentifierSemantic::canReferColumnToTable(right, tables[i].table);
-            if (match > right_best.first)
-            {
-                right_best.first = match;
-                right_best.second = i;
-            }
-        }
-
-        if (left_best.first && right_best.first && (left_best.second != right_best.second))
-        {
-            size_t table_pos = std::max(left_best.second, right_best.second);
-            if (tables[table_pos].canAttachOnExpression())
+            size_t table_pos = std::max(left_table_pos, right_table_pos);
+            if (joined_tables[table_pos].canAttachOnExpression())
                 return table_pos;
         }
         return 0;
@@ -212,27 +201,17 @@ private:
 
     size_t checkIdentifier(const ASTIdentifier & identifier)
     {
-        size_t best_match = 0;
         size_t best_table_pos = 0;
+        bool match = IdentifierSemantic::chooseTable(identifier, tables, best_table_pos);
 
-        for (size_t i = 0; i < tables.size(); ++i)
-        {
-            size_t match = IdentifierSemantic::canReferColumnToTable(identifier, tables[i].table);
-            if (match > best_match)
-            {
-                best_match = match;
-                best_table_pos = i;
-            }
-        }
-
-        if (best_match && tables[best_table_pos].canAttachOnExpression())
+        if (match && joined_tables[best_table_pos].canAttachOnExpression())
             return best_table_pos;
         return 0;
     }
 };
 
-using CheckExpressionMatcher = OneTypeMatcher<CheckExpressionVisitorData, false>;
-using CheckExpressionVisitor = InDepthNodeVisitor<CheckExpressionMatcher, true>;
+using CheckExpressionMatcher = ConstOneTypeMatcher<CheckExpressionVisitorData, false>;
+using CheckExpressionVisitor = ConstInDepthNodeVisitor<CheckExpressionMatcher, true>;
 
 
 bool getTables(ASTSelectQuery & select, std::vector<JoinedTable> & joined_tables, size_t & num_comma)
@@ -314,7 +293,7 @@ void CrossToInnerJoinMatcher::visit(ASTSelectQuery & select, ASTPtr &, Data & da
         return;
 
     CheckExpressionVisitor::Data visitor_data{joined_tables};
-    CheckExpressionVisitor(visitor_data).visit(select.refWhere());
+    CheckExpressionVisitor(visitor_data).visit(select.where());
 
     if (visitor_data.complex())
         return;

dbms/src/Interpreters/ExecuteScalarSubqueriesVisitor.cpp

@@ -6,14 +6,17 @@
 #include <Parsers/ASTExpressionList.h>
 
 #include <Interpreters/Context.h>
-#include <Interpreters/QueryNormalizer.h>
+#include <Interpreters/misc.h>
 #include <Interpreters/InterpreterSelectWithUnionQuery.h>
 #include <Interpreters/ExecuteScalarSubqueriesVisitor.h>
 #include <Interpreters/addTypeConversionToAST.h>
 
 #include <DataStreams/IBlockInputStream.h>
+#include <DataStreams/materializeBlock.h>
 #include <DataTypes/DataTypeAggregateFunction.h>
+#include <DataTypes/DataTypeTuple.h>
 
+#include <Columns/ColumnTuple.h>
 
 namespace DB
 {
@@ -53,69 +56,98 @@ void ExecuteScalarSubqueriesMatcher::visit(ASTPtr & ast, Data & data)
         visit(*t, ast, data);
 }
 
+/// Converting to literal values might take a fair amount of overhead when the value is large, (e.g.
+///  Array, BitMap, etc.), This conversion is required for constant folding, index lookup, branch
+///  elimination. However, these optimizations should never be related to large values, thus we
+///  blacklist them here.
+static bool worthConvertingToLiteral(const Block & scalar)
+{
+    auto scalar_type_name = scalar.safeGetByPosition(0).type->getFamilyName();
+    std::set<String> useless_literal_types = {"Array", "Tuple", "AggregateFunction", "Function", "Set", "LowCardinality"};
+    return !useless_literal_types.count(scalar_type_name);
+}
+
 void ExecuteScalarSubqueriesMatcher::visit(const ASTSubquery & subquery, ASTPtr & ast, Data & data)
 {
-    Context subquery_context = data.context;
-    Settings subquery_settings = data.context.getSettings();
-    subquery_settings.max_result_rows = 1;
-    subquery_settings.extremes = 0;
-    subquery_context.setSettings(subquery_settings);
+    auto hash = subquery.getTreeHash();
+    auto scalar_query_hash_str = toString(hash.first) + "_" + toString(hash.second);
 
-    ASTPtr subquery_select = subquery.children.at(0);
-    BlockIO res = InterpreterSelectWithUnionQuery(
-        subquery_select, subquery_context, SelectQueryOptions(QueryProcessingStage::Complete, data.subquery_depth + 1)).execute();
-
-    Block block;
-    try
+    Block scalar;
+    if (data.context.hasQueryContext() && data.context.getQueryContext().hasScalar(scalar_query_hash_str))
+        scalar = data.context.getQueryContext().getScalar(scalar_query_hash_str);
+    else if (data.scalars.count(scalar_query_hash_str))
+        scalar = data.scalars[scalar_query_hash_str];
+    else
     {
-        block = res.in->read();
+        Context subquery_context = data.context;
+        Settings subquery_settings = data.context.getSettings();
+        subquery_settings.max_result_rows = 1;
+        subquery_settings.extremes = 0;
+        subquery_context.setSettings(subquery_settings);
 
-        if (!block)
+        ASTPtr subquery_select = subquery.children.at(0);
+        BlockIO res = InterpreterSelectWithUnionQuery(
+                subquery_select, subquery_context, SelectQueryOptions(QueryProcessingStage::Complete, data.subquery_depth + 1)).execute();
+
+        Block block;
+        try
         {
-            /// Interpret subquery with empty result as Null literal
-            auto ast_new = std::make_unique<ASTLiteral>(Null());
-            ast_new->setAlias(ast->tryGetAlias());
-            ast = std::move(ast_new);
-            return;
+            block = res.in->read();
+
+            if (!block)
+            {
+                /// Interpret subquery with empty result as Null literal
+                auto ast_new = std::make_unique<ASTLiteral>(Null());
+                ast_new->setAlias(ast->tryGetAlias());
+                ast = std::move(ast_new);
+                return;
+            }
+
+            if (block.rows() != 1 || res.in->read())
+                throw Exception("Scalar subquery returned more than one row", ErrorCodes::INCORRECT_RESULT_OF_SCALAR_SUBQUERY);
+        }
+        catch (const Exception & e)
+        {
+            if (e.code() == ErrorCodes::TOO_MANY_ROWS)
+                throw Exception("Scalar subquery returned more than one row", ErrorCodes::INCORRECT_RESULT_OF_SCALAR_SUBQUERY);
+            else
+                throw;
         }
 
-        if (block.rows() != 1 || res.in->read())
-            throw Exception("Scalar subquery returned more than one row", ErrorCodes::INCORRECT_RESULT_OF_SCALAR_SUBQUERY);
-    }
-    catch (const Exception & e)
-    {
-        if (e.code() == ErrorCodes::TOO_MANY_ROWS)
-            throw Exception("Scalar subquery returned more than one row", ErrorCodes::INCORRECT_RESULT_OF_SCALAR_SUBQUERY);
+        block = materializeBlock(block);
+        size_t columns = block.columns();
+
+        if (columns == 1)
+            scalar = block;
         else
-            throw;
+        {
+
+            ColumnWithTypeAndName ctn;
+            ctn.type = std::make_shared<DataTypeTuple>(block.getDataTypes());
+            ctn.column = ColumnTuple::create(block.getColumns());
+            scalar.insert(ctn);
+        }
     }
 
-    size_t columns = block.columns();
-    if (columns == 1)
+    const Settings & settings = data.context.getSettingsRef();
+
+    // Always convert to literals when there is no query context.
+    if (!settings.enable_scalar_subquery_optimization || worthConvertingToLiteral(scalar) || !data.context.hasQueryContext())
     {
-        auto lit = std::make_unique<ASTLiteral>((*block.safeGetByPosition(0).column)[0]);
+        auto lit = std::make_unique<ASTLiteral>((*scalar.safeGetByPosition(0).column)[0]);
         lit->alias = subquery.alias;
         lit->prefer_alias_to_column_name = subquery.prefer_alias_to_column_name;
-        ast = addTypeConversionToAST(std::move(lit), block.safeGetByPosition(0).type->getName());
+        ast = addTypeConversionToAST(std::move(lit), scalar.safeGetByPosition(0).type->getName());
     }
     else
     {
-        auto tuple = std::make_shared<ASTFunction>();
-        tuple->alias = subquery.alias;
-        ast = tuple;
-        tuple->name = "tuple";
-        auto exp_list = std::make_shared<ASTExpressionList>();
-        tuple->arguments = exp_list;
-        tuple->children.push_back(tuple->arguments);
-
-        exp_list->children.resize(columns);
-        for (size_t i = 0; i < columns; ++i)
-        {
-            exp_list->children[i] = addTypeConversionToAST(
-                std::make_unique<ASTLiteral>((*block.safeGetByPosition(i).column)[0]),
-                block.safeGetByPosition(i).type->getName());
-        }
+        auto func = makeASTFunction("__getScalar", std::make_shared<ASTLiteral>(scalar_query_hash_str));
+        func->alias = subquery.alias;
+        func->prefer_alias_to_column_name = subquery.prefer_alias_to_column_name;
+        ast = std::move(func);
     }
+
+    data.scalars[scalar_query_hash_str] = std::move(scalar);
 }
 
 void ExecuteScalarSubqueriesMatcher::visit(const ASTFunction & func, ASTPtr & ast, Data & data)

dbms/src/Interpreters/ExecuteScalarSubqueriesVisitor.h

@@ -1,6 +1,7 @@
 #pragma once
 
 #include <Common/typeid_cast.h>
+#include <Core/Block.h>
 #include <Interpreters/InDepthNodeVisitor.h>
 
 namespace DB
@@ -36,6 +37,7 @@ public:
     {
         const Context & context;
         size_t subquery_depth;
+        Scalars & scalars;
     };
 
     static bool needChildVisit(ASTPtr & node, const ASTPtr &);

dbms/src/Interpreters/ExpressionAnalyzer.cpp

@@ -54,7 +54,7 @@
 #include <Parsers/queryToString.h>
 #include <Interpreters/interpretSubquery.h>
 #include <Interpreters/DatabaseAndTableWithAlias.h>
-#include <Interpreters/QueryNormalizer.h>
+#include <Interpreters/misc.h>
 
 #include <Interpreters/ActionsVisitor.h>
 

dbms/src/Interpreters/ExternalDictionariesLoader.cpp

@@ -1,17 +1,16 @@
 #include <Interpreters/ExternalDictionariesLoader.h>
 #include <Interpreters/Context.h>
 #include <Dictionaries/DictionaryFactory.h>
+#include <Dictionaries/getDictionaryConfigurationFromAST.h>
 
 namespace DB
 {
 
 /// Must not acquire Context lock in constructor to avoid possibility of deadlocks.
-ExternalDictionariesLoader::ExternalDictionariesLoader(
-    ExternalLoaderConfigRepositoryPtr config_repository, Context & context_)
+ExternalDictionariesLoader::ExternalDictionariesLoader(Context & context_)
     : ExternalLoader("external dictionary", &Logger::get("ExternalDictionariesLoader"))
     , context(context_)
 {
-    addConfigRepository(std::move(config_repository), {"dictionary", "name"});
     enableAsyncLoading(true);
     enablePeriodicUpdates(true);
 }
@@ -23,4 +22,21 @@ ExternalLoader::LoadablePtr ExternalDictionariesLoader::create(
     return DictionaryFactory::instance().create(name, config, key_in_config, context);
 }
 
+void ExternalDictionariesLoader::addConfigRepository(
+    const std::string & repository_name, std::unique_ptr<IExternalLoaderConfigRepository> config_repository)
+{
+    ExternalLoader::addConfigRepository(repository_name, std::move(config_repository), {"dictionary", "name"});
+}
+
+
+void ExternalDictionariesLoader::addDictionaryWithConfig(
+    const String & dictionary_name, const String & repo_name, const ASTCreateQuery & query, bool load_never_loading) const
+{
+    ExternalLoader::addObjectAndLoad(
+        dictionary_name, /// names are equal
+        dictionary_name,
+        repo_name,
+        getDictionaryConfigurationFromAST(query),
+        "dictionary", load_never_loading);
+}
 }

dbms/src/Interpreters/ExternalDictionariesLoader.h

@@ -4,6 +4,7 @@
 #include <Interpreters/IExternalLoaderConfigRepository.h>
 #include <Interpreters/ExternalLoader.h>
 #include <common/logger_useful.h>
+#include <Parsers/ASTCreateQuery.h>
 #include <memory>
 
 
@@ -19,9 +20,7 @@ public:
     using DictPtr = std::shared_ptr<const IDictionaryBase>;
 
     /// Dictionaries will be loaded immediately and then will be updated in separate thread, each 'reload_period' seconds.
-    ExternalDictionariesLoader(
-        ExternalLoaderConfigRepositoryPtr config_repository,
-        Context & context_);
+    ExternalDictionariesLoader(Context & context_);
 
     DictPtr getDictionary(const std::string & name) const
     {
@@ -33,6 +32,18 @@ public:
         return std::static_pointer_cast<const IDictionaryBase>(tryGetLoadable(name));
     }
 
+    void addConfigRepository(
+        const std::string & repository_name,
+        std::unique_ptr<IExternalLoaderConfigRepository> config_repository);
+
+    /// Starts reloading of a specified object.
+    void addDictionaryWithConfig(
+        const String & dictionary_name,
+        const String & repo_name,
+        const ASTCreateQuery & query,
+        bool load_never_loading = false) const;
+
+
 protected:
     LoadablePtr create(const std::string & name, const Poco::Util::AbstractConfiguration & config,
                        const std::string & key_in_config) const override;

dbms/src/Interpreters/ExternalLoader.cpp

@@ -20,12 +20,29 @@ namespace ErrorCodes
     extern const int BAD_ARGUMENTS;
 }
 
+namespace
+{
+
+/// Lock mutex only in async mode
+/// In other case does nothing
+struct LoadingGuardForAsyncLoad
+{
+    std::unique_lock<std::mutex> lock;
+    LoadingGuardForAsyncLoad(bool async, std::mutex & mutex)
+    {
+        if (async)
+            lock = std::unique_lock(mutex);
+    }
+};
+
+}
 
 struct ExternalLoader::ObjectConfig
 {
     String config_path;
     Poco::AutoPtr<Poco::Util::AbstractConfiguration> config;
     String key_in_config;
+    String repository_name;
 };
 
 
@@ -40,26 +57,84 @@ public:
     }
     ~LoadablesConfigReader() = default;
 
-    void addConfigRepository(std::unique_ptr<IExternalLoaderConfigRepository> repository, const ExternalLoaderConfigSettings & settings)
+    void addConfigRepository(
+        const String & name,
+        std::unique_ptr<IExternalLoaderConfigRepository> repository,
+        const ExternalLoaderConfigSettings & settings)
     {
         std::lock_guard lock{mutex};
-        repositories.emplace_back(std::move(repository), std::move(settings));
+        repositories.emplace(name, std::make_pair(std::move(repository), settings));
+    }
+
+    void removeConfigRepository(const String & name)
+    {
+        std::lock_guard lock{mutex};
+        repositories.erase(name);
     }
 
     using ObjectConfigsPtr = std::shared_ptr<const std::unordered_map<String /* object's name */, ObjectConfig>>;
 
-    /// Reads configuration files.
+
+    /// Reads configurations.
     ObjectConfigsPtr read()
     {
-        std::lock_guard lock{mutex};
-
+        std::lock_guard lock(mutex);
         // Check last modification times of files and read those files which are new or changed.
         if (!readLoadablesInfos())
             return configs; // Nothing changed, so we can return the previous result.
 
+        return collectConfigs();
+    }
+
+    ObjectConfig updateLoadableInfo(
+        const String & external_name,
+        const String & object_name,
+        const String & repo_name,
+        const Poco::AutoPtr<Poco::Util::AbstractConfiguration> & config,
+        const String & key)
+    {
+        std::lock_guard lock(mutex);
+
+        auto it = loadables_infos.find(object_name);
+        if (it == loadables_infos.end())
+        {
+            LoadablesInfos loadable_info;
+            loadables_infos[object_name] = loadable_info;
+        }
+        auto & loadable_info = loadables_infos[object_name];
+        ObjectConfig object_config{object_name, config, key, repo_name};
+        bool found = false;
+        for (auto iter = loadable_info.configs.begin(); iter != loadable_info.configs.end(); ++iter)
+        {
+            if (iter->first == external_name)
+            {
+                iter->second = object_config;
+                found = true;
+                break;
+            }
+        }
+
+        if (!found)
+            loadable_info.configs.emplace_back(external_name, object_config);
+        loadable_info.last_update_time = Poco::Timestamp{}; /// now
+        loadable_info.in_use = true;
+        return object_config;
+    }
+
+private:
+    struct LoadablesInfos
+    {
+        Poco::Timestamp last_update_time = 0;
+        std::vector<std::pair<String, ObjectConfig>> configs; // Parsed loadable's contents.
+        bool in_use = true; // Whether the `LoadablesInfos` should be destroyed because the correspondent loadable is deleted.
+    };
+
+    /// Collect current configurations
+    ObjectConfigsPtr collectConfigs()
+    {
         // Generate new result.
         auto new_configs = std::make_shared<std::unordered_map<String /* object's name */, ObjectConfig>>();
-        for (const auto & [path, loadable_info] :  loadables_infos)
+        for (const auto & [path, loadable_info] : loadables_infos)
         {
             for (const auto & [name, config] : loadable_info.configs)
             {
@@ -81,14 +156,6 @@ public:
         return configs;
     }
 
-private:
-    struct  LoadablesInfos
-    {
-        Poco::Timestamp last_update_time = 0;
-        std::vector<std::pair<String, ObjectConfig>> configs; // Parsed file's contents.
-        bool in_use = true; // Whether the ` LoadablesInfos` should be destroyed because the correspondent file is deleted.
-    };
-
     /// Read files and store them to the map ` loadables_infos`.
     bool readLoadablesInfos()
     {
@@ -100,58 +167,59 @@ private:
             loadable_info.in_use = false;
         }
 
-        for (const auto & [repository, settings] : repositories)
+        for (const auto & [repo_name, repo_with_settings] : repositories)
         {
-            const auto names = repository->getAllLoadablesDefinitionNames();
-            for (const auto & name : names)
+            const auto names = repo_with_settings.first->getAllLoadablesDefinitionNames();
+            for (const auto & loadable_name : names)
             {
-                auto it =  loadables_infos.find(name);
-                if (it !=  loadables_infos.end())
+                auto it = loadables_infos.find(loadable_name);
+                if (it != loadables_infos.end())
                 {
                     LoadablesInfos & loadable_info = it->second;
-                    if (readLoadablesInfo(*repository, name, settings, loadable_info))
+                    if (readLoadablesInfo(repo_name, *repo_with_settings.first, loadable_name, repo_with_settings.second, loadable_info))
                         changed = true;
                 }
                 else
                 {
                     LoadablesInfos loadable_info;
-                    if (readLoadablesInfo(*repository, name, settings, loadable_info))
+                    if (readLoadablesInfo(repo_name, *repo_with_settings.first, loadable_name, repo_with_settings.second, loadable_info))
                     {
-                        loadables_infos.emplace(name, std::move(loadable_info));
+                        loadables_infos.emplace(loadable_name, std::move(loadable_info));
                         changed = true;
                     }
                 }
             }
         }
 
-        std::vector<String> deleted_files;
+        std::vector<String> deleted_names;
         for (auto & [path, loadable_info] : loadables_infos)
             if (!loadable_info.in_use)
-                deleted_files.emplace_back(path);
-        if (!deleted_files.empty())
+                deleted_names.emplace_back(path);
+        if (!deleted_names.empty())
         {
-            for (const String & deleted_file : deleted_files)
-                loadables_infos.erase(deleted_file);
+            for (const String & deleted_name : deleted_names)
+                loadables_infos.erase(deleted_name);
             changed = true;
         }
         return changed;
     }
 
     bool readLoadablesInfo(
+        const String & repo_name,
         IExternalLoaderConfigRepository & repository,
-        const String & path,
+        const String & object_name,
         const ExternalLoaderConfigSettings & settings,
         LoadablesInfos & loadable_info) const
     {
         try
         {
-            if (path.empty() || !repository.exists(path))
+            if (object_name.empty() || !repository.exists(object_name))
             {
-                LOG_WARNING(log, "config file '" + path + "' does not exist");
+                LOG_WARNING(log, "Config file '" + object_name + "' does not exist");
                 return false;
             }
 
-            auto update_time_from_repository = repository.getUpdateTime(path);
+            auto update_time_from_repository = repository.getUpdateTime(object_name);
 
             /// Actually it can't be less, but for sure we check less or equal
             if (update_time_from_repository <= loadable_info.last_update_time)
@@ -160,31 +228,31 @@ private:
                 return false;
             }
 
-            auto file_contents = repository.load(path);
+            auto file_contents = repository.load(object_name);
 
             /// get all objects' definitions
             Poco::Util::AbstractConfiguration::Keys keys;
             file_contents->keys(keys);
 
-            /// for each object defined in xml config
+            /// for each object defined in repositories
             std::vector<std::pair<String, ObjectConfig>> configs_from_file;
             for (const auto & key : keys)
             {
                 if (!startsWith(key, settings.external_config))
                 {
                     if (!startsWith(key, "comment") && !startsWith(key, "include_from"))
-                        LOG_WARNING(log, path << ": file contains unknown node '" << key << "', expected '" << settings.external_config << "'");
+                        LOG_WARNING(log, object_name << ": file contains unknown node '" << key << "', expected '" << settings.external_config << "'");
                     continue;
                 }
 
-                String name = file_contents->getString(key + "." + settings.external_name);
-                if (name.empty())
+                String external_name = file_contents->getString(key + "." + settings.external_name);
+                if (external_name.empty())
                 {
-                    LOG_WARNING(log, path << ": node '" << key << "' defines " << type_name << " with an empty name. It's not allowed");
+                    LOG_WARNING(log, object_name << ": node '" << key << "' defines " << type_name << " with an empty name. It's not allowed");
                     continue;
                 }
 
-                configs_from_file.emplace_back(name, ObjectConfig{path, file_contents, key});
+                configs_from_file.emplace_back(external_name, ObjectConfig{object_name, file_contents, key, repo_name});
             }
 
             loadable_info.configs = std::move(configs_from_file);
@@ -194,16 +262,19 @@ private:
         }
         catch (...)
         {
-            tryLogCurrentException(log, "Failed to read config file '" + path + "'");
+            tryLogCurrentException(log, "Failed to load config for dictionary '" + object_name + "'");
             return false;
         }
     }
 
+
     const String type_name;
     Logger * log;
 
     std::mutex mutex;
-    std::vector<std::pair<std::unique_ptr<IExternalLoaderConfigRepository>, ExternalLoaderConfigSettings>> repositories;
+    using RepositoryPtr = std::unique_ptr<IExternalLoaderConfigRepository>;
+    using RepositoryWithSettings = std::pair<RepositoryPtr, ExternalLoaderConfigSettings>;
+    std::unordered_map<String, RepositoryWithSettings> repositories;
     ObjectConfigsPtr configs;
     std::unordered_map<String /* config path */, LoadablesInfos>  loadables_infos;
 };
@@ -267,10 +338,10 @@ public:
             else
             {
                 const auto & new_config = new_config_it->second;
-                if (!isSameConfiguration(*info.config.config, info.config.key_in_config, *new_config.config, new_config.key_in_config))
+                if (!isSameConfiguration(*info.object_config.config, info.object_config.key_in_config, *new_config.config, new_config.key_in_config))
                 {
                     /// Configuration has been changed.
-                    info.config = new_config;
+                    info.object_config = new_config;
                     info.config_changed = true;
 
                     if (info.wasLoading())
@@ -305,6 +376,12 @@ public:
         event.notify_all();
     }
 
+    void setSingleObjectConfigurationWithoutLoading(const String & external_name, const ObjectConfig & config)
+    {
+        std::lock_guard lock{mutex};
+        infos.emplace(external_name, Info{config});
+    }
+
     /// Sets whether all the objects from the configuration should be always loaded (even if they aren't used).
     void enableAlwaysLoadEverything(bool enable)
     {
@@ -326,7 +403,6 @@ public:
     /// Sets whether the objects should be loaded asynchronously, each loading in a new thread (from the thread pool).
     void enableAsyncLoading(bool enable)
     {
-        std::lock_guard lock{mutex};
         enable_async_loading = enable;
     }
 
@@ -432,8 +508,17 @@ public:
         loaded_objects = collectLoadedObjects(filter_by_name);
     }
 
+    /// Tries to finish loading of the objects for which the specified function returns true.
+    void load(const FilterByNameFunction & filter_by_name, LoadResults & loaded_results, Duration timeout = NO_TIMEOUT)
+    {
+        std::unique_lock lock{mutex};
+        loadImpl(filter_by_name, timeout, lock);
+        loaded_results = collectLoadResults(filter_by_name);
+    }
+
     /// Tries to finish loading of all the objects during the timeout.
     void load(Loadables & loaded_objects, Duration timeout = NO_TIMEOUT) { load(allNames, loaded_objects, timeout); }
+    void load(LoadResults & loaded_results, Duration timeout = NO_TIMEOUT) { load(allNames, loaded_results, timeout); }
 
     /// Starts reloading a specified object.
     void reload(const String & name, bool load_never_loading = false)
@@ -441,7 +526,9 @@ public:
         std::lock_guard lock{mutex};
         Info * info = getInfo(name);
         if (!info)
+        {
             return;
+        }
 
         if (info->wasLoading() || load_never_loading)
         {
@@ -539,7 +626,7 @@ public:
 private:
     struct Info
     {
-        Info(const ObjectConfig & config_) : config(config_) {}
+        Info(const ObjectConfig & object_config_) : object_config(object_config_) {}
 
         bool loaded() const { return object != nullptr; }
         bool failed() const { return !object && exception; }
@@ -571,11 +658,12 @@ private:
             result.exception = exception;
             result.loading_start_time = loading_start_time;
             result.loading_duration = loadingDuration();
-            result.origin = config.config_path;
+            result.origin = object_config.config_path;
+            result.repository_name = object_config.repository_name;
             return result;
         }
 
-        ObjectConfig config;
+        ObjectConfig object_config;
         LoadablePtr object;
         TimePoint loading_start_time;
         TimePoint loading_end_time;
@@ -618,8 +706,10 @@ private:
         LoadResults load_results;
         load_results.reserve(infos.size());
         for (const auto & [name, info] : infos)
+        {
             if (filter_by_name(name))
                 load_results.emplace_back(name, info.loadResult());
+        }
         return load_results;
     }
 
@@ -691,48 +781,15 @@ private:
         }
     }
 
-    /// Does the loading, possibly in the separate thread.
-    void doLoading(const String & name, size_t loading_id, bool async)
+    /// Load one object, returns object ptr or exception
+    /// Do not require locking
+
+    std::pair<LoadablePtr, std::exception_ptr> loadOneObject(
+        const String & name,
+        const ObjectConfig & config,
+        bool config_changed,
+        LoadablePtr previous_version)
     {
-        std::unique_lock<std::mutex> lock;
-        if (async)
-        {
-            setThreadName("ExterLdrJob");
-            lock = std::unique_lock{mutex}; /// If `async == false` the mutex is already locked.
-        }
-
-        SCOPE_EXIT({
-            if (async)
-            {
-                if (!lock.owns_lock())
-                    lock.lock();
-                /// Remove the information about the thread after it finishes.
-                auto it = loading_ids.find(loading_id);
-                if (it != loading_ids.end())
-                {
-                    it->second.detach();
-                    loading_ids.erase(it);
-                }
-            }
-        });
-
-        /// We check here if this is exactly the same loading as we planned to perform.
-        /// This check is necessary because the object could be removed or load with another config before this thread even starts.
-        Info * info = getInfo(name);
-        if (!info || !info->loading() || (info->loading_id != loading_id))
-            return;
-
-        ObjectConfig config = info->config;
-        bool config_changed = info->config_changed;
-        LoadablePtr previous_version = info->object;
-        size_t error_count = info->error_count;
-
-        /// Use `create_function` to perform the actual loading.
-        /// It's much better to do it with `mutex` unlocked because the loading can take a lot of time
-        /// and require access to other objects.
-        if (async)
-            lock.unlock();
-
         LoadablePtr new_object;
         std::exception_ptr new_exception;
         try
@@ -743,10 +800,45 @@ private:
         {
             new_exception = std::current_exception();
         }
+        return std::make_pair(new_object, new_exception);
 
-        if (!new_object && !new_exception)
-            throw Exception("No object created and no exception raised for " + type_name, ErrorCodes::LOGICAL_ERROR);
+    }
 
+    /// Return single object info, checks loading_id and name
+    std::optional<Info> getSingleObjectInfo(const String & name, size_t loading_id, bool async)
+    {
+        LoadingGuardForAsyncLoad lock(async, mutex);
+        Info * info = getInfo(name);
+        if (!info || !info->loading() || (info->loading_id != loading_id))
+            return {};
+
+        return *info;
+    }
+
+    /// Removes object loading_id from loading_ids if it present
+    /// in other case do nothin should by done with lock
+    void finishObjectLoading(size_t loading_id, const LoadingGuardForAsyncLoad &)
+    {
+        auto it = loading_ids.find(loading_id);
+        if (it != loading_ids.end())
+        {
+            it->second.detach();
+            loading_ids.erase(it);
+        }
+    }
+
+    /// Process loading result
+    /// Calculates next update time and process errors
+    void processLoadResult(
+        const String & name,
+        size_t loading_id,
+        LoadablePtr previous_version,
+        LoadablePtr new_object,
+        std::exception_ptr new_exception,
+        size_t error_count,
+        bool async)
+    {
+        LoadingGuardForAsyncLoad lock(async, mutex);
         /// Calculate a new update time.
         TimePoint next_update_time;
         try
@@ -755,7 +847,12 @@ private:
                 ++error_count;
             else
                 error_count = 0;
-            next_update_time = calculateNextUpdateTime(new_object, error_count);
+
+            LoadablePtr object = previous_version;
+            if (new_object)
+                object = new_object;
+
+            next_update_time = calculateNextUpdateTime(object, error_count);
         }
         catch (...)
         {
@@ -763,10 +860,8 @@ private:
             next_update_time = TimePoint::max();
         }
 
-        /// Lock the mutex again to store the changes.
-        if (async)
-            lock.lock();
-        info = getInfo(name);
+
+        Info * info = getInfo(name);
 
         /// And again we should check if this is still the same loading as we were doing.
         /// This is necessary because the object could be removed or load with another config while the `mutex` was unlocked.
@@ -802,10 +897,38 @@ private:
         if (new_object)
             info->config_changed = false;
 
-        /// Notify `event` to recheck conditions in loadImpl() now.
-        if (async)
-            lock.unlock();
-        event.notify_all();
+        finishObjectLoading(loading_id, lock);
+    }
+
+
+    /// Does the loading, possibly in the separate thread.
+    void doLoading(const String & name, size_t loading_id, bool async)
+    {
+        try
+        {
+            /// We check here if this is exactly the same loading as we planned to perform.
+            /// This check is necessary because the object could be removed or load with another config before this thread even starts.
+            std::optional<Info> info = getSingleObjectInfo(name, loading_id, async);
+            if (!info)
+                return;
+
+            /// Use `create_function` to perform the actual loading.
+            /// It's much better to do it with `mutex` unlocked because the loading can take a lot of time
+            /// and require access to other objects.
+            auto [new_object, new_exception] = loadOneObject(name, info->object_config, info->config_changed, info->object);
+            if (!new_object && !new_exception)
+                throw Exception("No object created and no exception raised for " + type_name, ErrorCodes::LOGICAL_ERROR);
+
+
+            processLoadResult(name, loading_id, info->object, new_object, new_exception, info->error_count, async);
+            event.notify_all();
+        }
+        catch (...)
+        {
+            LoadingGuardForAsyncLoad lock(async, mutex);
+            finishObjectLoading(loading_id, lock);
+            throw;
+        }
     }
 
     void cancelLoading(const String & name)
@@ -844,7 +967,8 @@ private:
     TimePoint calculateNextUpdateTime(const LoadablePtr & loaded_object, size_t error_count) const
     {
         static constexpr auto never = TimePoint::max();
-        if (!error_count)
+
+        if (loaded_object)
         {
             if (!loaded_object->supportUpdates())
                 return never;
@@ -854,8 +978,11 @@ private:
             if (lifetime.min_sec == 0 || lifetime.max_sec == 0)
                 return never;
 
-            std::uniform_int_distribution<UInt64> distribution{lifetime.min_sec, lifetime.max_sec};
-            return std::chrono::system_clock::now() + std::chrono::seconds{distribution(rnd_engine)};
+            if (!error_count)
+            {
+                std::uniform_int_distribution<UInt64> distribution{lifetime.min_sec, lifetime.max_sec};
+                return std::chrono::system_clock::now() + std::chrono::seconds{distribution(rnd_engine)};
+            }
         }
 
         return std::chrono::system_clock::now() + std::chrono::seconds(calculateDurationWithBackoff(rnd_engine, error_count));
@@ -870,7 +997,7 @@ private:
     ObjectConfigsPtr configs;
     std::unordered_map<String, Info> infos;
     bool always_load_everything = false;
-    bool enable_async_loading = false;
+    std::atomic<bool> enable_async_loading = false;
     std::unordered_map<size_t, ThreadFromGlobalPool> loading_ids;
     size_t next_loading_id = 1; /// should always be > 0
     mutable pcg64 rnd_engine{randomSeed()};
@@ -956,12 +1083,19 @@ ExternalLoader::ExternalLoader(const String & type_name_, Logger * log)
 ExternalLoader::~ExternalLoader() = default;
 
 void ExternalLoader::addConfigRepository(
-    std::unique_ptr<IExternalLoaderConfigRepository> config_repository, const ExternalLoaderConfigSettings & config_settings)
+    const std::string & repository_name,
+    std::unique_ptr<IExternalLoaderConfigRepository> config_repository,
+    const ExternalLoaderConfigSettings & config_settings)
 {
-    config_files_reader->addConfigRepository(std::move(config_repository), config_settings);
+    config_files_reader->addConfigRepository(repository_name, std::move(config_repository), config_settings);
     loading_dispatcher->setConfiguration(config_files_reader->read());
 }
 
+void ExternalLoader::removeConfigRepository(const std::string & repository_name)
+{
+    config_files_reader->removeConfigRepository(repository_name);
+}
+
 void ExternalLoader::enableAlwaysLoadEverything(bool enable)
 {
     loading_dispatcher->enableAlwaysLoadEverything(enable);
@@ -1035,23 +1169,52 @@ void ExternalLoader::load(const FilterByNameFunction & filter_by_name, Loadables
         loading_dispatcher->load(loaded_objects, timeout);
 }
 
+
+void ExternalLoader::load(const FilterByNameFunction & filter_by_name, LoadResults & loaded_objects, Duration timeout) const
+{
+    if (filter_by_name)
+        loading_dispatcher->load(filter_by_name, loaded_objects, timeout);
+    else
+        loading_dispatcher->load(loaded_objects, timeout);
+}
+
+
 void ExternalLoader::load(Loadables & loaded_objects, Duration timeout) const
 {
     return loading_dispatcher->load(loaded_objects, timeout);
 }
 
-void ExternalLoader::reload(const String & name, bool load_never_loading)
+void ExternalLoader::reload(const String & name, bool load_never_loading) const
 {
-    loading_dispatcher->setConfiguration(config_files_reader->read());
+    auto configs = config_files_reader->read();
+    loading_dispatcher->setConfiguration(configs);
     loading_dispatcher->reload(name, load_never_loading);
 }
 
-void ExternalLoader::reload(bool load_never_loading)
+void ExternalLoader::reload(bool load_never_loading) const
 {
     loading_dispatcher->setConfiguration(config_files_reader->read());
     loading_dispatcher->reload(load_never_loading);
 }
 
+void ExternalLoader::addObjectAndLoad(
+    const String & name,
+    const String & external_name,
+    const String & repo_name,
+    const Poco::AutoPtr<Poco::Util::AbstractConfiguration> & config,
+    const String & key,
+    bool load_never_loading) const
+{
+    auto object_config = config_files_reader->updateLoadableInfo(external_name, name, repo_name, config, key);
+    loading_dispatcher->setSingleObjectConfigurationWithoutLoading(external_name, object_config);
+    LoadablePtr loaded_object;
+    if (load_never_loading)
+        loading_dispatcher->loadStrict(name, loaded_object);
+    else
+        loading_dispatcher->load(name, loaded_object, Duration::zero());
+}
+
+
 ExternalLoader::LoadablePtr ExternalLoader::createObject(
     const String & name, const ObjectConfig & config, bool config_changed, const LoadablePtr & previous_version) const
 {

dbms/src/Interpreters/ExternalLoader.h

@@ -72,6 +72,7 @@ public:
         TimePoint loading_start_time;
         Duration loading_duration;
         std::exception_ptr exception;
+        std::string repository_name;
     };
 
     using LoadResults = std::vector<std::pair<String, LoadResult>>;
@@ -81,7 +82,12 @@ public:
 
     /// Adds a repository which will be used to read configurations from.
     void addConfigRepository(
-        std::unique_ptr<IExternalLoaderConfigRepository> config_repository, const ExternalLoaderConfigSettings & config_settings);
+        const std::string & repository_name,
+        std::unique_ptr<IExternalLoaderConfigRepository> config_repository,
+        const ExternalLoaderConfigSettings & config_settings);
+
+    /// Removes a repository which were used to read configurations.
+    void removeConfigRepository(const std::string & repository_name);
 
     /// Sets whether all the objects from the configuration should be always loaded (even those which are never used).
     void enableAlwaysLoadEverything(bool enable);
@@ -132,6 +138,7 @@ public:
 
     /// Tries to finish loading of the objects for which the specified function returns true.
     void load(const FilterByNameFunction & filter_by_name, Loadables & loaded_objects, Duration timeout = NO_TIMEOUT) const;
+    void load(const FilterByNameFunction & filter_by_name, LoadResults & load_results, Duration timeout = NO_TIMEOUT) const;
     Loadables loadAndGet(const FilterByNameFunction & filter_by_name, Duration timeout = NO_TIMEOUT) const { Loadables loaded_objects; load(filter_by_name, loaded_objects, timeout); return loaded_objects; }
 
     /// Tries to finish loading of all the objects during the timeout.
@@ -140,16 +147,27 @@ public:
     /// Starts reloading of a specified object.
     /// `load_never_loading` specifies what to do if the object has never been loading before.
     /// The function can either skip it (false) or load for the first time (true).
-    void reload(const String & name, bool load_never_loading = false);
+    /// Also function can load dictionary synchronously
+    void reload(const String & name, bool load_never_loading = false) const;
+
 
     /// Starts reloading of all the objects.
     /// `load_never_loading` specifies what to do with the objects which have never been loading before.
     /// The function can either skip them (false) or load for the first time (true).
-    void reload(bool load_never_loading = false);
+    void reload(bool load_never_loading = false) const;
 
 protected:
     virtual LoadablePtr create(const String & name, const Poco::Util::AbstractConfiguration & config, const String & key_in_config) const = 0;
 
+    /// Reload object with already parsed configuration
+    void addObjectAndLoad(
+        const String & name, /// name of dictionary
+        const String & external_name, /// name of source (example xml-file, may contain more than dictionary)
+        const String & repo_name, /// name of repository (database name, or all xml files)
+        const Poco::AutoPtr<Poco::Util::AbstractConfiguration> & config,
+        const String & key_in_config, /// key where we can start search of loadables (<dictionary>, <model>, etc)
+        bool load_never_loading = false) const;
+
 private:
     struct ObjectConfig;
 

dbms/src/Interpreters/ExternalLoaderDatabaseConfigRepository.cpp

@@ -0,0 +1,56 @@
+#include <Interpreters/ExternalLoaderDatabaseConfigRepository.h>
+#include <Dictionaries/getDictionaryConfigurationFromAST.h>
+
+namespace DB
+{
+
+namespace ErrorCodes
+{
+    extern const int UNKNOWN_DICTIONARY;
+}
+
+namespace
+{
+String trimDatabaseName(const std::string & loadable_definition_name, const DatabasePtr database)
+{
+    const auto & dbname = database->getDatabaseName();
+    if (!startsWith(loadable_definition_name, dbname))
+        throw Exception(
+            "Loadable '" + loadable_definition_name + "' is not from database '" + database->getDatabaseName(), ErrorCodes::UNKNOWN_DICTIONARY);
+    ///    dbname.loadable_name
+    ///--> remove <---
+    return loadable_definition_name.substr(dbname.length() + 1);
+}
+}
+
+LoadablesConfigurationPtr ExternalLoaderDatabaseConfigRepository::load(const std::string & loadable_definition_name) const
+{
+    String dictname = trimDatabaseName(loadable_definition_name, database);
+    return getDictionaryConfigurationFromAST(database->getCreateDictionaryQuery(context, dictname)->as<const ASTCreateQuery &>());
+}
+
+bool ExternalLoaderDatabaseConfigRepository::exists(const std::string & loadable_definition_name) const
+{
+    return database->isDictionaryExist(
+                     context, trimDatabaseName(loadable_definition_name, database));
+}
+
+Poco::Timestamp ExternalLoaderDatabaseConfigRepository::getUpdateTime(const std::string & loadable_definition_name)
+{
+    return database->getObjectMetadataModificationTime(context, trimDatabaseName(loadable_definition_name, database));
+}
+
+std::set<std::string> ExternalLoaderDatabaseConfigRepository::getAllLoadablesDefinitionNames() const
+{
+    std::set<std::string> result;
+    const auto & dbname = database->getDatabaseName();
+    auto itr = database->getDictionariesIterator(context);
+    while (itr && itr->isValid())
+    {
+        result.insert(dbname + "." + itr->name());
+        itr->next();
+    }
+    return result;
+}
+
+}

dbms/src/Interpreters/ExternalLoaderDatabaseConfigRepository.h

@@ -0,0 +1,34 @@
+#pragma once
+
+#include <Interpreters/IExternalLoaderConfigRepository.h>
+#include <Databases/IDatabase.h>
+#include <Interpreters/Context.h>
+
+namespace DB
+{
+
+/// Repository from database, which stores dictionary definitions on disk.
+/// Tracks update time and existance of .sql files through IDatabase.
+class ExternalLoaderDatabaseConfigRepository : public IExternalLoaderConfigRepository
+{
+public:
+    ExternalLoaderDatabaseConfigRepository(const DatabasePtr & database_, const Context & context_)
+        : database(database_)
+        , context(context_)
+    {
+    }
+
+    std::set<std::string> getAllLoadablesDefinitionNames() const override;
+
+    bool exists(const std::string & loadable_definition_name) const override;
+
+    Poco::Timestamp getUpdateTime(const std::string & loadable_definition_name) override;
+
+    LoadablesConfigurationPtr load(const std::string & loadable_definition_name) const override;
+
+private:
+    DatabasePtr database;
+    Context context;
+};
+
+}