BlockIO InterpreterCreateQuery::createTable(ASTCreateQuery & create) { if (!create.cluster.empty()) { NameSet databases{create.database}; if (!create.to_table.empty()) databases.emplace(create.to_database); return executeDDLQueryOnCluster(query_ptr, context, std::move(databases)); } String path = context.getPath(); String current_database = context.getCurrentDatabase(); String database_name = create.database.empty() ? current_database : create.database; String table_name = create.table; String table_name_escaped = escapeForFileName(table_name); // If this is a stub ATTACH query, read the query definition from the database if (create.attach && !create.storage && !create.columns) { // Table SQL definition is available even if the table is detached auto query = context.getCreateTableQuery(database_name, table_name); auto & as_create = typeid_cast<const ASTCreateQuery &>(*query); create = as_create; // Copy the saved create query, but use ATTACH instead of CREATE create.attach = true; } if (create.to_database.empty()) create.to_database = current_database; if (create.select && (create.is_view || create.is_materialized_view)) { AddDefaultDatabaseVisitor visitor(current_database); visitor.visit(*create.select); } Block as_select_sample; if (create.select && (!create.attach || !create.columns)) as_select_sample = InterpreterSelectWithUnionQuery::getSampleBlock(create.select->clone(), context); String as_database_name = create.as_database.empty() ? current_database : create.as_database; String as_table_name = create.as_table; StoragePtr as_storage; TableStructureReadLockPtr as_storage_lock; if (!as_table_name.empty()) { as_storage = context.getTable(as_database_name, as_table_name); as_storage_lock = as_storage->lockStructure(false); } /// Set and retrieve list of columns. ColumnsDescription columns = setColumns(create, as_select_sample, as_storage); /// Some column types may be not allowed according to settings. if (!create.attach) checkSupportedTypes(columns, context); /// Set the table engine if it was not specified explicitly. setEngine(create); StoragePtr res; { std::unique_ptr<DDLGuard> guard; String data_path; DatabasePtr database; if (!create.temporary) { database = context.getDatabase(database_name); data_path = database->getDataPath(); /** If the request specifies IF NOT EXISTS, we allow concurrent CREATE queries (which do nothing). * If table doesnt exist, one thread is creating table, while others wait in DDLGuard. */ guard = context.getDDLGuard(database_name, table_name); /// Table can be created before or it can be created concurrently in another thread, while we were waiting in DDLGuard. if (database->isTableExist(context, table_name)) { if (create.if_not_exists) return {}; else throw Exception("Table " + database_name + "." + table_name + " already exists.", ErrorCodes::TABLE_ALREADY_EXISTS); } } else if (context.tryGetExternalTable(table_name) && create.if_not_exists) return {}; res = StorageFactory::instance().get(create, data_path, table_name, database_name, context, context.getGlobalContext(), columns, create.attach, false); if (create.temporary) context.getSessionContext().addExternalTable(table_name, res, query_ptr); else database->createTable(context, table_name, res, query_ptr); /// We must call "startup" and "shutdown" while holding DDLGuard. /// Because otherwise method "shutdown" (from InterpreterDropQuery) can be called before startup /// (in case when table was created and instantly dropped before started up) /// /// Method "startup" may create background tasks and method "shutdown" will wait for them. /// But if "shutdown" is called before "startup", it will exit early, because there are no background tasks to wait. /// Then background task is created by "startup" method. And when destructor of a table object is called, background task is still active, /// and the task will use references to freed data. res->startup(); } /// If the query is a CREATE SELECT, insert the data into the table. if (create.select && !create.attach && !create.is_view && (!create.is_materialized_view || create.is_populate)) { auto insert = std::make_shared<ASTInsertQuery>(); if (!create.temporary) insert->database = database_name; insert->table = table_name; insert->select = create.select->clone(); if (create.temporary && !context.getSessionContext().hasQueryContext()) context.getSessionContext().setQueryContext(context.getSessionContext()); return InterpreterInsertQuery(insert, create.temporary ? context.getSessionContext() : context, context.getSettingsRef().insert_allow_materialized_columns).execute(); } return {}; }
BlockIO InterpreterCreateQuery::createTable(ASTCreateQuery & create) { if (!create.cluster.empty()) { NameSet databases{create.database}; if (!create.to_table.empty()) databases.emplace(create.to_database); return executeDDLQueryOnCluster(query_ptr, context, databases); } String path = context.getPath(); String current_database = context.getCurrentDatabase(); String database_name = create.database.empty() ? current_database : create.database; String table_name = create.table; String table_name_escaped = escapeForFileName(table_name); // If this is a stub ATTACH query, read the query definition from the database if (create.attach && !create.storage && !create.columns) { // Table SQL definition is available even if the table is detached auto query = context.getCreateTableQuery(database_name, table_name); auto & as_create = typeid_cast<const ASTCreateQuery &>(*query); create = as_create; // Copy the saved create query, but use ATTACH instead of CREATE create.attach = true; } if (create.to_database.empty()) create.to_database = current_database; if (create.select && (create.is_view || create.is_materialized_view)) create.select->setDatabaseIfNeeded(current_database); Block as_select_sample; if (create.select && (!create.attach || !create.columns)) as_select_sample = InterpreterSelectWithUnionQuery::getSampleBlock(create.select->clone(), context); String as_database_name = create.as_database.empty() ? current_database : create.as_database; String as_table_name = create.as_table; StoragePtr as_storage; TableStructureReadLockPtr as_storage_lock; if (!as_table_name.empty()) { as_storage = context.getTable(as_database_name, as_table_name); as_storage_lock = as_storage->lockStructure(false, __PRETTY_FUNCTION__); } /// Set and retrieve list of columns. ColumnsDescription columns = setColumns(create, as_select_sample, as_storage); /// Set the table engine if it was not specified explicitly. setEngine(create); StoragePtr res; { std::unique_ptr<DDLGuard> guard; String data_path; DatabasePtr database; if (!create.is_temporary) { database = context.getDatabase(database_name); data_path = database->getDataPath(); /** If the table already exists, and the request specifies IF NOT EXISTS, * then we allow concurrent CREATE queries (which do nothing). * Otherwise, concurrent queries for creating a table, if the table does not exist, * can throw an exception, even if IF NOT EXISTS is specified. */ guard = context.getDDLGuardIfTableDoesntExist(database_name, table_name, "Table " + database_name + "." + table_name + " is creating or attaching right now"); if (!guard) { if (create.if_not_exists) return {}; else throw Exception("Table " + database_name + "." + table_name + " already exists.", ErrorCodes::TABLE_ALREADY_EXISTS); } } else if (context.tryGetExternalTable(table_name) && create.if_not_exists) return {}; res = StorageFactory::instance().get(create, data_path, table_name, database_name, context, context.getGlobalContext(), columns, create.attach, false); if (create.is_temporary) context.getSessionContext().addExternalTable(table_name, res, query_ptr); else database->createTable(context, table_name, res, query_ptr); } res->startup(); /// If the query is a CREATE SELECT, insert the data into the table. if (create.select && !create.attach && !create.is_view && (!create.is_materialized_view || create.is_populate)) { auto insert = std::make_shared<ASTInsertQuery>(); if (!create.is_temporary) insert->database = database_name; insert->table = table_name; insert->select = create.select->clone(); return InterpreterInsertQuery(insert, create.is_temporary ? context.getSessionContext() : context, context.getSettingsRef().insert_allow_materialized_columns).execute(); } return {}; }