Fix error with Lazy database

src/Databases/IDatabase.h

@@ -40,6 +40,10 @@ public:
     virtual bool isValid() const = 0;
 
     virtual const String & name() const = 0;
+
+    /// This method can return nullptr if it's Lazy database
+    /// (a database with support for lazy tables loading
+    /// - it maintains a list of tables but tables are loaded lazily).
     virtual const StoragePtr & table() const = 0;
 
     virtual ~IDatabaseTablesIterator() = default;

src/Interpreters/ActionLocksManager.cpp

@@ -29,7 +29,8 @@ inline void forEachTable(F && f, const Context & context)
 {
     for (auto & elem : DatabaseCatalog::instance().getDatabases())
         for (auto iterator = elem.second->getTablesIterator(context); iterator->isValid(); iterator->next())
-            f(iterator->table());
+            if (auto table = iterator->table())
+                f(table);
 
 }
 

src/Interpreters/AsynchronousMetrics.cpp

@@ -185,6 +185,9 @@ void AsynchronousMetrics::update()
             {
                 ++total_number_of_tables;
                 const auto & table = iterator->table();
+                if (!table)
+                    continue;
+
                 StorageMergeTree * table_merge_tree = dynamic_cast<StorageMergeTree *>(table.get());
                 StorageReplicatedMergeTree * table_replicated_merge_tree = dynamic_cast<StorageReplicatedMergeTree *>(table.get());
 

src/Interpreters/InterpreterSystemQuery.cpp

@@ -376,8 +376,11 @@ void InterpreterSystemQuery::restartReplicas(Context & system_context)
         DatabasePtr & database = elem.second;
         for (auto iterator = database->getTablesIterator(context); iterator->isValid(); iterator->next())
         {
-            if (dynamic_cast<const StorageReplicatedMergeTree *>(iterator->table().get()))
-                replica_names.emplace_back(StorageID{database->getDatabaseName(), iterator->name()});
+            if (auto table = iterator->table())
+            {
+                if (dynamic_cast<const StorageReplicatedMergeTree *>(table.get()))
+                    replica_names.emplace_back(StorageID{database->getDatabaseName(), iterator->name()});
+            }
         }
     }
 

src/Server/ReplicasStatusHandler.cpp

@@ -47,6 +47,9 @@ void ReplicasStatusHandler::handleRequest(Poco::Net::HTTPServerRequest & request
             for (auto iterator = db.second->getTablesIterator(context); iterator->isValid(); iterator->next())
             {
                 const auto & table = iterator->table();
+                if (!table)
+                    continue;
+
                 StorageReplicatedMergeTree * table_replicated = dynamic_cast<StorageReplicatedMergeTree *>(table.get());
 
                 if (!table_replicated)

src/Storages/StorageMerge.cpp

@@ -79,7 +79,7 @@ StoragePtr StorageMerge::getFirstTable(F && predicate) const
 
 bool StorageMerge::isRemote() const
 {
-    auto first_remote_table = getFirstTable([](const StoragePtr & table) { return table->isRemote(); });
+    auto first_remote_table = getFirstTable([](const StoragePtr & table) { return table && table->isRemote(); });
     return first_remote_table != nullptr;
 }
 
@@ -117,7 +117,7 @@ QueryProcessingStage::Enum StorageMerge::getQueryProcessingStage(const Context &
     while (iterator->isValid())
     {
         const auto & table = iterator->table();
-        if (table.get() != this)
+        if (table && table.get() != this)
         {
             ++selected_table_size;
             stage_in_source_tables = std::max(stage_in_source_tables, table->getQueryProcessingStage(context, to_stage, query_ptr));
@@ -316,7 +316,7 @@ StorageMerge::StorageListWithLocks StorageMerge::getSelectedTables(const String
     while (iterator->isValid())
     {
         const auto & table = iterator->table();
-        if (table.get() != this)
+        if (table && table.get() != this)
             selected_tables.emplace_back(
                     table, table->lockStructureForShare(false, query_id, settings.lock_acquire_timeout), iterator->name());
 
@@ -338,6 +338,8 @@ StorageMerge::StorageListWithLocks StorageMerge::getSelectedTables(
     while (iterator->isValid())
     {
         StoragePtr storage = iterator->table();
+        if (!storage)
+            continue;
 
         if (query && query->as<ASTSelectQuery>()->prewhere() && !storage->supportsPrewhere())
             throw Exception("Storage " + storage->getName() + " doesn't support PREWHERE.", ErrorCodes::ILLEGAL_PREWHERE);
@@ -495,7 +497,7 @@ NamesAndTypesList StorageMerge::getVirtuals() const
 {
     NamesAndTypesList virtuals{{"_table", std::make_shared<DataTypeString>()}};
 
-    auto first_table = getFirstTable([](auto &&) { return true; });
+    auto first_table = getFirstTable([](auto && table) { return table; });
     if (first_table)
     {
         auto table_virtuals = first_table->getVirtuals();

src/Storages/System/StorageSystemColumns.cpp

@@ -303,12 +303,15 @@ Pipes StorageSystemColumns::read(
 
             for (auto iterator = database->getTablesIterator(context); iterator->isValid(); iterator->next())
             {
-                const String & table_name = iterator->name();
-                storages.emplace(std::piecewise_construct,
-                    std::forward_as_tuple(database_name, table_name),
-                    std::forward_as_tuple(iterator->table()));
-                table_column_mut->insert(table_name);
-                ++offsets[i];
+                if (const auto & table = iterator->table())
+                {
+                    const String & table_name = iterator->name();
+                    storages.emplace(std::piecewise_construct,
+                        std::forward_as_tuple(database_name, table_name),
+                        std::forward_as_tuple(table));
+                    table_column_mut->insert(table_name);
+                    ++offsets[i];
+                }
             }
         }
 

src/Storages/System/StorageSystemGraphite.cpp

@@ -39,6 +39,8 @@ static StorageSystemGraphite::Configs getConfigs(const Context & context)
         for (auto iterator = db.second->getTablesIterator(context); iterator->isValid(); iterator->next())
         {
             const auto & table = iterator->table();
+            if (!table)
+                continue;
 
             const MergeTreeData * table_data = dynamic_cast<const MergeTreeData *>(table.get());
             if (!table_data)

src/Storages/System/StorageSystemMutations.cpp

@@ -53,13 +53,17 @@ void StorageSystemMutations::fillData(MutableColumns & res_columns, const Contex
 
         for (auto iterator = db.second->getTablesIterator(context); iterator->isValid(); iterator->next())
         {
-            if (!dynamic_cast<const MergeTreeData *>(iterator->table().get()))
+            const auto & table = iterator->table();
+            if (!table)
+                continue;
+
+            if (!dynamic_cast<const MergeTreeData *>(table.get()))
                 continue;
 
             if (check_access_for_tables && !access->isGranted(AccessType::SHOW_TABLES, db.first, iterator->name()))
                 continue;
 
-            merge_tree_tables[db.first][iterator->name()] = iterator->table();
+            merge_tree_tables[db.first][iterator->name()] = table;
         }
     }
 

src/Storages/System/StorageSystemPartsBase.cpp

@@ -115,6 +115,9 @@ StoragesInfoStream::StoragesInfoStream(const SelectQueryInfo & query_info, const
                 {
                     String table_name = iterator->name();
                     StoragePtr storage = iterator->table();
+                    if (!storage)
+                        continue;
+
                     String engine_name = storage->getName();
 
                     if (!dynamic_cast<MergeTreeData *>(storage.get()))

src/Storages/System/StorageSystemReplicas.cpp

@@ -78,11 +78,15 @@ Pipes StorageSystemReplicas::read(
         const bool check_access_for_tables = check_access_for_databases && !access->isGranted(AccessType::SHOW_TABLES, db.first);
         for (auto iterator = db.second->getTablesIterator(context); iterator->isValid(); iterator->next())
         {
-            if (!dynamic_cast<const StorageReplicatedMergeTree *>(iterator->table().get()))
+            const auto & table = iterator->table();
+            if (!table)
+                continue;
+
+            if (!dynamic_cast<const StorageReplicatedMergeTree *>(table.get()))
                 continue;
             if (check_access_for_tables && !access->isGranted(AccessType::SHOW_TABLES, db.first, iterator->name()))
                 continue;
-            replicated_tables[db.first][iterator->name()] = iterator->table();
+            replicated_tables[db.first][iterator->name()] = table;
         }
     }
 

src/Storages/System/StorageSystemReplicationQueue.cpp

@@ -62,11 +62,14 @@ void StorageSystemReplicationQueue::fillData(MutableColumns & res_columns, const
 
         for (auto iterator = db.second->getTablesIterator(context); iterator->isValid(); iterator->next())
         {
-            if (!dynamic_cast<const StorageReplicatedMergeTree *>(iterator->table().get()))
+            const auto & table = iterator->table();
+            if (!table)
+                continue;
+            if (!dynamic_cast<const StorageReplicatedMergeTree *>(table.get()))
                 continue;
             if (check_access_for_tables && !access->isGranted(AccessType::SHOW_TABLES, db.first, iterator->name()))
                 continue;
-            replicated_tables[db.first][iterator->name()] = iterator->table();
+            replicated_tables[db.first][iterator->name()] = table;
         }
     }
 

src/TableFunctions/TableFunctionMerge.cpp

@@ -34,7 +34,8 @@ static NamesAndTypesList chooseColumns(const String & source_database, const Str
         auto iterator = database->getTablesIterator(context, table_name_match);
 
         if (iterator->isValid())
-            any_table = iterator->table();
+            if (const auto & table = iterator->table())
+                any_table = table;
     }
 
     if (!any_table)

tests/queries/0_stateless/01294_lazy_database_concurrent_recreate_reattach_and_show_tables.sh

@@ -0,0 +1,109 @@
+#!/usr/bin/env bash
+
+CURDIR=$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)
+. $CURDIR/../shell_config.sh
+
+export CURR_DATABASE="test_lazy_01294_concurrent_${CLICKHOUSE_DATABASE}"
+
+
+function recreate_lazy_func1()
+{
+    $CLICKHOUSE_CLIENT -q "
+        CREATE TABLE $CURR_DATABASE.log (a UInt64, b UInt64) ENGINE = Log;
+    ";
+
+    while true; do
+        $CLICKHOUSE_CLIENT -q "
+            DETACH TABLE $CURR_DATABASE.log;
+        ";
+
+        $CLICKHOUSE_CLIENT -q "
+            ATTACH TABLE $CURR_DATABASE.log;
+        ";
+        done
+}
+
+function recreate_lazy_func2()
+{
+    while true; do
+        $CLICKHOUSE_CLIENT -q "
+            CREATE TABLE $CURR_DATABASE.tlog (a UInt64, b UInt64) ENGINE = TinyLog;
+        ";
+
+        $CLICKHOUSE_CLIENT -q "
+            DROP TABLE $CURR_DATABASE.tlog;
+        ";
+        done
+}
+
+function recreate_lazy_func3()
+{
+    $CLICKHOUSE_CLIENT -q "
+        CREATE TABLE $CURR_DATABASE.slog (a UInt64, b UInt64) ENGINE = StripeLog;
+    ";
+
+    while true; do
+        $CLICKHOUSE_CLIENT -q "
+            ATTACH TABLE $CURR_DATABASE.slog;
+        ";
+
+        $CLICKHOUSE_CLIENT -q "
+            DETACH TABLE $CURR_DATABASE.slog;
+        ";
+        done
+}
+
+function recreate_lazy_func4()
+{
+    while true; do
+        $CLICKHOUSE_CLIENT -q "
+            CREATE TABLE $CURR_DATABASE.tlog2 (a UInt64, b UInt64) ENGINE = TinyLog;
+        ";
+
+        $CLICKHOUSE_CLIENT -q "
+            DROP TABLE $CURR_DATABASE.tlog2;
+        ";
+        done
+}
+
+function test_func()
+{
+    while true; do
+        $CLICKHOUSE_CLIENT -q "SYSTEM STOP TTL MERGES";
+        done
+}
+
+
+export -f recreate_lazy_func1;
+export -f recreate_lazy_func2;
+export -f recreate_lazy_func3;
+export -f recreate_lazy_func4;
+export -f test_func;
+
+
+${CLICKHOUSE_CLIENT} -n -q "
+    DROP DATABASE IF EXISTS $CURR_DATABASE;
+    CREATE DATABASE $CURR_DATABASE ENGINE = Lazy(1);
+"
+
+
+TIMEOUT=30
+
+timeout $TIMEOUT bash -c recreate_lazy_func1 2> /dev/null &
+timeout $TIMEOUT bash -c recreate_lazy_func2 2> /dev/null &
+timeout $TIMEOUT bash -c recreate_lazy_func3 2> /dev/null &
+timeout $TIMEOUT bash -c recreate_lazy_func4 2> /dev/null &
+timeout $TIMEOUT bash -c test_func 2> /dev/null &
+
+wait
+sleep 1
+
+${CLICKHOUSE_CLIENT} -n -q "
+    DROP TABLE IF EXISTS $CURR_DATABASE.log;
+    DROP TABLE IF EXISTS $CURR_DATABASE.slog;
+    DROP TABLE IF EXISTS $CURR_DATABASE.tlog;
+    DROP TABLE IF EXISTS $CURR_DATABASE.tlog2;
+"
+
+$CLICKHOUSE_CLIENT -q "SYSTEM START TTL MERGES";
+echo "Test OK"