Adding DETACH TABLE PERMANENTLY

src/Databases/DatabaseOnDisk.cpp

@@ -170,14 +170,19 @@ void DatabaseOnDisk::createTable(
     if (isTableExist(table_name, global_context))
         throw Exception("Table " + backQuote(getDatabaseName()) + "." + backQuote(table_name) + " already exists.", ErrorCodes::TABLE_ALREADY_EXISTS);
 
-    if (create.attach_short_syntax)
+    String table_metadata_path = getObjectMetadataPath(table_name);
+
+    if (create.attach_short_syntax && Poco::File(table_metadata_path).exists())
     {
-        /// Metadata already exists, table was detached
+        /// Metadata already exists, table was detached (not permanently)
         attachTable(table_name, table, getTableDataPath(create));
         return;
+
+        /// if the table was detached permanently, then usual metadata file doesn't exists
+        /// (.sql_detached instead) and we use longer, but safer way of attaching that back
+        /// with recreating the metadata file.
     }
 
-    String table_metadata_path = getObjectMetadataPath(table_name);
     String table_metadata_tmp_path = table_metadata_path + create_suffix;
     String statement;
 
@@ -213,8 +218,47 @@ void DatabaseOnDisk::commitCreateTable(const ASTCreateQuery & query, const Stora
         Poco::File(table_metadata_tmp_path).remove();
         throw;
     }
+
+    try
+    {
+        /// If the table was detached permanently we will have a file with
+        /// .sql_detached suffix, which is not needed anymore since we attached the table back
+        auto table_metadata_file_detached = Poco::File(table_metadata_path + detached_suffix);
+        if (table_metadata_file_detached.exists())
+            table_metadata_file_detached.remove();
+    }
+    catch (...)
+    {
+        // It's not a big issue if we can't remove the .sql_detached file.
+        LOG_WARNING(log, getCurrentExceptionMessage(__PRETTY_FUNCTION__));
+    }
 }
 
+void DatabaseOnDisk::detachTablePermanently(const String & table_name)
+{
+    StoragePtr table = detachTable(table_name);
+
+    /// This is possible for Lazy database.
+    if (!table)
+        return;
+
+    String table_metadata_path = getObjectMetadataPath(table_name);
+    String table_metadata_path_detached = table_metadata_path + detached_suffix;
+
+    try
+    {
+        /// it will silently overwrite the file if exists, and it's ok
+        Poco::File(table_metadata_path).renameTo(table_metadata_path_detached);
+    }
+    catch (Exception & e)
+    {
+        e.addMessage("while trying to detach table {} permanently.", table_name);
+        throw;
+    }
+
+}
+
+
 void DatabaseOnDisk::dropTable(const Context & context, const String & table_name, bool /*no_delay*/)
 {
     String table_metadata_path = getObjectMetadataPath(table_name);
@@ -328,14 +372,22 @@ void DatabaseOnDisk::renameTable(
     }
 }
 
+
+/// It returns create table statement (even if table is detached permanently)
 ASTPtr DatabaseOnDisk::getCreateTableQueryImpl(const String & table_name, const Context &, bool throw_on_error) const
 {
     ASTPtr ast;
     bool has_table = tryGetTable(table_name, global_context) != nullptr;
     auto table_metadata_path = getObjectMetadataPath(table_name);
+
     try
     {
-        ast = getCreateQueryFromMetadata(table_metadata_path, throw_on_error);
+        if (Poco::File(table_metadata_path).exists())
+            ast = getCreateQueryFromMetadata(table_metadata_path, throw_on_error);
+        else if (Poco::File(table_metadata_path + detached_suffix).exists())
+            ast = getCreateQueryFromMetadata(table_metadata_path + detached_suffix, throw_on_error);
+        else if (throw_on_error)
+            throw Exception("Metadata file does not exist", ErrorCodes::FILE_DOESNT_EXIST);
     }
     catch (const Exception & e)
     {
@@ -430,6 +482,10 @@ void DatabaseOnDisk::iterateMetadataFiles(const Context & context, const Iterati
         if (endsWith(dir_it.name(), ".sql.bak"))
             continue;
 
+        /// Permanently detached tables are not attached automatically
+        if (endsWith(dir_it.name(), ".sql_detached"))
+            continue;
+
         static const char * tmp_drop_ext = ".sql.tmp_drop";
         if (endsWith(dir_it.name(), tmp_drop_ext))
         {
@@ -510,6 +566,8 @@ ASTPtr DatabaseOnDisk::parseQueryFromMetadata(Poco::Logger * logger, const Conte
     auto & create = ast->as<ASTCreateQuery &>();
     if (!create.table.empty() && create.uuid != UUIDHelpers::Nil)
     {
+        /// if the table is detached permanently getBaseName will still return a proper name
+        /// because we use table_name.sql_detached naming
         String table_name = Poco::Path(metadata_file_path).makeFile().getBaseName();
         table_name = unescapeForFileName(table_name);
 

src/Databases/DatabaseOnDisk.h

@@ -39,6 +39,8 @@ public:
         const StoragePtr & table,
         const ASTPtr & query) override;
 
+    void detachTablePermanently(const String & table_name) override;
+
     void dropTable(
         const Context & context,
         const String & table_name,
@@ -71,6 +73,11 @@ protected:
     static constexpr const char * create_suffix = ".tmp";
     static constexpr const char * drop_suffix = ".tmp_drop";
 
+    /// engine=Atomic takes the table name from basename of metadata file (also for detached table)
+    /// in case of double dots (table_name.sql.detached) it would extract 'table_name.sql'
+    /// so we use simpler option "table_name.sql_detached" and get 'table_name' correctly.
+    static constexpr const char * detached_suffix = "_detached";
+
     using IteratingFunction = std::function<void(const String &)>;
 
     void iterateMetadataFiles(const Context & context, const IteratingFunction & process_metadata_file) const;

src/Databases/IDatabase.h

@@ -221,6 +221,8 @@ public:
     }
 
     /// Add a table to the database, but do not add it to the metadata. The database may not support this method.
+    ///
+    /// Note: ATTACH TABLE statement actually uses createTable method.
     virtual void attachTable(const String & /*name*/, const StoragePtr & /*table*/, [[maybe_unused]] const String & relative_table_path = {})
     {
         throw Exception("There is no ATTACH TABLE query for Database" + getEngineName(), ErrorCodes::NOT_IMPLEMENTED);
@@ -245,6 +247,13 @@ public:
         throw Exception("There is no DETACH DICTIONARY query for Database" + getEngineName(), ErrorCodes::NOT_IMPLEMENTED);
     }
 
+    /// Forget about the table without deleting it's data, but rename metadata file to prevent reloading it
+    /// with next restart. The database may not support this method.
+    virtual void detachTablePermanently(const String & /*name*/)
+    {
+        throw Exception("There is no DETACH TABLE PERMANENTLY query for Database" + getEngineName(), ErrorCodes::NOT_IMPLEMENTED);
+    }
+
     /// Rename the table and possibly move the table to another database.
     virtual void renameTable(
         const Context & /*context*/,

src/Interpreters/InterpreterCreateQuery.cpp

@@ -734,7 +734,7 @@ BlockIO InterpreterCreateQuery::createTable(ASTCreateQuery & create)
         auto database = DatabaseCatalog::instance().getDatabase(database_name);
         bool if_not_exists = create.if_not_exists;
 
-        // Table SQL definition is available even if the table is detached
+        // Table SQL definition is available even if the table is detached (even permanently)
         auto query = database->getCreateTableQuery(create.table, context);
         create = query->as<ASTCreateQuery &>(); // Copy the saved create query, but use ATTACH instead of CREATE
         if (create.is_dictionary)

src/Interpreters/InterpreterDropQuery.cpp

@@ -128,8 +128,18 @@ BlockIO InterpreterDropQuery::executeToTableImpl(const ASTDropQuery & query, Dat
             TableExclusiveLockHolder table_lock;
             if (database->getUUID() == UUIDHelpers::Nil)
                 table_lock = table->lockExclusively(context.getCurrentQueryId(), context.getSettingsRef().lock_acquire_timeout);
-            /// Drop table from memory, don't touch data and metadata
-            database->detachTable(table_id.table_name);
+
+            if (query.permanently)
+            {
+                /// Drop table from memory, don't touch data, metadata file renamed and will be skipped during server restart
+                database->detachTablePermanently(table_id.table_name);
+            }
+            else
+            {
+                /// Drop table from memory, don't touch data and metadata
+                database->detachTable(table_id.table_name);
+            }
+
         }
         else if (query.kind == ASTDropQuery::Kind::Truncate)
         {

src/Interpreters/loadMetadata.cpp

@@ -108,6 +108,7 @@ void loadMetadata(Context & context, const String & default_database_name)
 
         if (!it->isDirectory())
         {
+            /// TODO: DETACH DATABASE PERMANENTLY ?
             if (endsWith(it.name(), ".sql"))
             {
                 String db_name = it.name().substr(0, it.name().size() - 4);

src/Parsers/ASTDropQuery.cpp

@@ -67,6 +67,9 @@ void ASTDropQuery::formatQueryImpl(const FormatSettings & settings, FormatState
 
     formatOnCluster(settings);
 
+    if (permanently)
+        settings.ostr << " PERMANENTLY";
+
     if (no_delay)
         settings.ostr << (settings.hilite ? hilite_keyword : "") << " NO DELAY" << (settings.hilite ? hilite_none : "");
 }

src/Parsers/ASTDropQuery.h

@@ -33,6 +33,9 @@ public:
 
     bool no_delay{false};
 
+    // We detach the object permanently, so it will not be reattached back during server restart.
+    bool permanently{false};
+
     /** Get the text that identifies this element. */
     String getID(char) const override;
     ASTPtr clone() const override;

src/Parsers/ParserDropQuery.cpp

@@ -21,6 +21,7 @@ bool parseDropQuery(IParser::Pos & pos, ASTPtr & node, Expected & expected, bool
     ParserToken s_dot(TokenType::Dot);
     ParserKeyword s_if_exists("IF EXISTS");
     ParserIdentifier name_p;
+    ParserKeyword s_permanently("PERMANENTLY");
     ParserKeyword s_no_delay("NO DELAY");
     ParserKeyword s_sync("SYNC");
 
@@ -32,6 +33,7 @@ bool parseDropQuery(IParser::Pos & pos, ASTPtr & node, Expected & expected, bool
     bool is_dictionary = false;
     bool is_view = false;
     bool no_delay = false;
+    bool permanently = false;
 
     if (s_database.ignore(pos, expected))
     {
@@ -83,6 +85,9 @@ bool parseDropQuery(IParser::Pos & pos, ASTPtr & node, Expected & expected, bool
                 return false;
         }
 
+        if (s_permanently.ignore(pos, expected))
+            permanently = true;
+
         if (s_no_delay.ignore(pos, expected) || s_sync.ignore(pos, expected))
             no_delay = true;
     }
@@ -96,6 +101,7 @@ bool parseDropQuery(IParser::Pos & pos, ASTPtr & node, Expected & expected, bool
     query->is_dictionary = is_dictionary;
     query->is_view = is_view;
     query->no_delay = no_delay;
+    query->permanently = permanently;
 
     tryGetIdentifierNameInto(database, query->database);
     tryGetIdentifierNameInto(table, query->table);

src/Parsers/ParserDropQuery.h

@@ -8,7 +8,7 @@ namespace DB
 {
 
 /** Query like this:
-  * DROP|DETACH|TRUNCATE TABLE [IF EXISTS] [db.]name
+  * DROP|DETACH|TRUNCATE TABLE [IF EXISTS] [db.]name [PERMANENTLY]
   *
   * Or:
   * DROP DATABASE [IF EXISTS] db

tests/queries/0_stateless/01600_detach_permanently.reference

@@ -0,0 +1,84 @@
+#####
+db_ordinary.log_table 1
+>table detached!
+db_ordinary.log_table 2
+>Table is back after restart
+10
+db_ordinary.log_table 3
+>table detached (permanently)!
+db_ordinary.log_table 4
+>table is still detached (after restart)!
+db_ordinary.log_table 5
+>Table is back after attach
+db_ordinary.log_table 6
+10
+#####
+db_ordinary.mt_table 1
+>table detached!
+db_ordinary.mt_table 2
+>Table is back after restart
+10
+db_ordinary.mt_table 3
+>table detached (permanently)!
+db_ordinary.mt_table 4
+>table is still detached (after restart)!
+db_ordinary.mt_table 5
+>Table is back after attach
+db_ordinary.mt_table 6
+10
+#####
+db_ordinary.null_table 1
+>table detached!
+db_ordinary.null_table 2
+>Table is back after restart
+0
+db_ordinary.null_table 3
+>table detached (permanently)!
+db_ordinary.null_table 4
+>table is still detached (after restart)!
+db_ordinary.null_table 5
+>Table is back after attach
+db_ordinary.null_table 6
+0
+#####
+db_atomic.log_table 1
+>table detached!
+db_atomic.log_table 2
+>Table is back after restart
+10
+db_atomic.log_table 3
+>table detached (permanently)!
+db_atomic.log_table 4
+>table is still detached (after restart)!
+db_atomic.log_table 5
+>Table is back after attach
+db_atomic.log_table 6
+10
+#####
+db_atomic.mt_table 1
+>table detached!
+db_atomic.mt_table 2
+>Table is back after restart
+10
+db_atomic.mt_table 3
+>table detached (permanently)!
+db_atomic.mt_table 4
+>table is still detached (after restart)!
+db_atomic.mt_table 5
+>Table is back after attach
+db_atomic.mt_table 6
+10
+#####
+db_atomic.null_table 1
+>table detached!
+db_atomic.null_table 2
+>Table is back after restart
+0
+db_atomic.null_table 3
+>table detached (permanently)!
+db_atomic.null_table 4
+>table is still detached (after restart)!
+db_atomic.null_table 5
+>Table is back after attach
+db_atomic.null_table 6
+0

tests/queries/0_stateless/01600_detach_permanently.sh

@@ -0,0 +1,72 @@
+#!/usr/bin/env bash
+
+CURDIR=$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)
+. "$CURDIR"/../shell_config.sh
+
+## tests with real clickhouse restart would be a bit to heavy,
+## to ensure the table will not reappear back clickhose-local is enough.
+
+# TODO: clean it...
+# CLICKHOUSE_LOCAL="/home/mfilimonov/workspace/ClickHouse-detach-permanently/build/programs/clickhouse-local"
+# CLICKHOUSE_TMP=$(pwd)
+
+WORKING_FOLDER_01600="${CLICKHOUSE_TMP}/01600_detach_permanently"
+rm -rf "${WORKING_FOLDER_01600}"
+mkdir -p "${WORKING_FOLDER_01600}"
+
+clickhouse_local() {
+    local query="$1"
+    shift
+    ${CLICKHOUSE_LOCAL} --query "$query" $@ -- --path="${WORKING_FOLDER_01600}"
+}
+
+test_detach_attach_sequence() {
+    local db="$1"
+    local table="$2"
+    echo "#####"
+
+    echo "${db}.${table} 1"
+    # normal DETACH - while process is running (clickhouse-local here, same for server) table is detached.
+    clickhouse_local "DETACH TABLE ${db}.${table}; SELECT if( count() = 0, '>table detached!', '>Fail') FROM system.tables WHERE database='${db}' AND name='${table}';"
+
+    # but once we restart the precess (either clickhouse-local either clickhouse server) the table is back.
+    echo "${db}.${table} 2"
+    clickhouse_local "SELECT if(name='${table}', '>Table is back after restart', '>fail') FROM system.tables WHERE database='${db}' AND name='${table}'; SELECT count() FROM ${db}.${table};"
+
+    # permanent DETACH - table is detached, and metadata file renamed, prevening further attach
+    echo "${db}.${table} 3"
+    clickhouse_local "DETACH TABLE ${db}.${table} PERMANENTLY; SELECT if( count() = 0, '>table detached (permanently)!', '>Fail') FROM system.tables WHERE database='${db}' AND name='${table}';"
+
+    # still detached after restart
+    echo "${db}.${table} 4"
+    clickhouse_local "SELECT if( count() = 0, '>table is still detached (after restart)!', '>Fail') FROM system.tables WHERE database='${db}' AND name='${table}';"
+
+    # but can be reattached
+    echo "${db}.${table} 5"
+    clickhouse_local "ATTACH TABLE ${db}.${table}; SELECT if(name='${table}', '>Table is back after attach', '>fail') FROM system.tables WHERE database='${db}' AND name='${table}';"
+
+    echo "${db}.${table} 6"
+    clickhouse_local "SELECT count() FROM ${db}.${table};"
+}
+
+clickhouse_local "DROP DATABASE IF EXISTS db_ordinary SYNC;"
+clickhouse_local "DROP DATABASE IF EXISTS db_atomic SYNC;"
+
+clickhouse_local "CREATE DATABASE db_ordinary Engine=Ordinary"
+clickhouse_local "CREATE DATABASE db_atomic Engine=Atomic"
+
+clickhouse_local "CREATE TABLE db_ordinary.log_table Engine=Log AS SELECT * FROM numbers(10)"
+clickhouse_local "CREATE TABLE db_ordinary.mt_table Engine=MergeTree ORDER BY tuple() AS SELECT * FROM numbers(10)"
+clickhouse_local "CREATE TABLE db_ordinary.null_table Engine=Null AS SELECT * FROM numbers(10)"
+
+clickhouse_local "CREATE TABLE db_atomic.log_table Engine=Log AS SELECT * FROM numbers(10)"
+clickhouse_local "CREATE TABLE db_atomic.mt_table Engine=MergeTree ORDER BY tuple() AS SELECT * FROM numbers(10)"
+clickhouse_local "CREATE TABLE db_atomic.null_table Engine=Null AS SELECT * FROM numbers(10)"
+
+test_detach_attach_sequence "db_ordinary" "log_table"
+test_detach_attach_sequence "db_ordinary" "mt_table"
+test_detach_attach_sequence "db_ordinary" "null_table"
+
+test_detach_attach_sequence "db_atomic" "log_table"
+test_detach_attach_sequence "db_atomic" "mt_table"
+test_detach_attach_sequence "db_atomic" "null_table"