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Bug#54678: InnoDB, TRUNCATE, ALTER, I_S SELECT, crash or deadlock - Incompatible change: truncate no longer resorts to a row by row delete if the storage engine does not support the truncate method. Consequently, the count of affected rows does not, in any case, reflect the actual number of rows. - Incompatible change: it is no longer possible to truncate a table that participates as a parent in a foreign key constraint, unless it is a self-referencing constraint (both parent and child are in the same table). To work around this incompatible change and still be able to truncate such tables, disable foreign checks with SET foreign_key_checks=0 before truncate. Alternatively, if foreign key checks are necessary, please use a DELETE statement without a WHERE condition. Problem description: The problem was that for storage engines that do not support truncate table via a external drop and recreate, such as InnoDB which implements truncate via a internal drop and recreate, the delete_all_rows method could be invoked with a shared metadata lock, causing problems if the engine needed exclusive access to some internal metadata. This problem originated with the fact that there is no truncate specific handler method, which ended up leading to a abuse of the delete_all_rows method that is primarily used for delete operations without a condition. Solution: The solution is to introduce a truncate handler method that is invoked when the engine does not support truncation via a table drop and recreate. This method is invoked under a exclusive metadata lock, so that there is only a single instance of the table when the method is invoked. Also, the method is not invoked and a error is thrown if the table is a parent in a non-self-referencing foreign key relationship. This was necessary to avoid inconsistency as some integrity checks are bypassed. This is inline with the fact that truncate is primarily a DDL operation that was designed to quickly remove all data from a table. mysql-test/suite/innodb/t/innodb-truncate.test: Add test cases for truncate and foreign key checks. Also test that InnoDB resets auto-increment on truncate. mysql-test/suite/innodb/t/innodb.test: FK is not necessary, test is related to auto-increment. Update error number, truncate is no longer invoked if table is parent in a FK relationship. mysql-test/suite/innodb/t/innodb_mysql.test: Update error number, truncate is no longer invoked if table is parent in a FK relationship. Use delete instead of truncate, test is used to check the interaction of FKs, triggers and delete. mysql-test/suite/parts/inc/partition_check.inc: Fix typo. mysql-test/suite/sys_vars/t/foreign_key_checks_func.test: Update error number, truncate is no longer invoked if table is parent in a FK relationship. mysql-test/t/mdl_sync.test: Modify test case to reflect and ensure that truncate takes a exclusive metadata lock. mysql-test/t/trigger-trans.test: Update error number, truncate is no longer invoked if table is parent in a FK relationship. sql/ha_partition.cc: Reorganize the various truncate methods. delete_all_rows is now passed directly to the underlying engines, so as truncate. The code responsible for truncating individual partitions is moved to ha_partition::truncate_partition, which is invoked when a ALTER TABLE t1 TRUNCATE PARTITION p statement is executed. Since the partition truncate no longer can be invoked via delete, the bitmap operations are not necessary anymore. The explicit reset of the auto-increment value is also removed as the underlying engines are now responsible for reseting the value. sql/handler.cc: Wire up the handler truncate method. sql/handler.h: Introduce and document the truncate handler method. It assumes certain use cases of delete_all_rows. Add method to retrieve the list of foreign keys referencing a table. Method is used to avoid truncating tables that are parent in a foreign key relationship. sql/share/errmsg-utf8.txt: Add error message for truncate and FK. sql/sql_lex.h: Introduce a flag so that the partition engine can detect when a partition is being truncated. Used to give a special error. sql/sql_parse.cc: Function mysql_truncate_table no longer exists. sql/sql_partition_admin.cc: Implement the TRUNCATE PARTITION statement. sql/sql_truncate.cc: Change the truncate table implementation to use the new truncate handler method and to not rely on row-by-row delete anymore. The truncate handler method is always invoked with a exclusive metadata lock. Also, it is no longer possible to truncate a table that is parent in some non-self-referencing foreign key. storage/archive/ha_archive.cc: Rename method as the description indicates that in the future this could be a truncate operation. storage/blackhole/ha_blackhole.cc: Implement truncate as no operation for the blackhole engine in order to remain compatible with older releases. storage/federated/ha_federated.cc: Introduce truncate method that invokes delete_all_rows. This is required to support partition truncate as this form of truncate does not implement the drop and recreate protocol. storage/heap/ha_heap.cc: Introduce truncate method that invokes delete_all_rows. This is required to support partition truncate as this form of truncate does not implement the drop and recreate protocol. storage/ibmdb2i/ha_ibmdb2i.cc: Introduce truncate method that invokes delete_all_rows. This is required to support partition truncate as this form of truncate does not implement the drop and recreate protocol. storage/innobase/handler/ha_innodb.cc: Rename delete_all_rows to truncate. InnoDB now does truncate under a exclusive metadata lock. Introduce and reorganize methods used to retrieve the list of foreign keys referenced by a or referencing a table. storage/myisammrg/ha_myisammrg.cc: Introduce truncate method that invokes delete_all_rows. This is required in order to remain compatible with earlier releases where truncate would resort to a row-by-row delete.
64 lines
1.9 KiB
C++
64 lines
1.9 KiB
C++
#ifndef SQL_TRUNCATE_INCLUDED
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#define SQL_TRUNCATE_INCLUDED
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/* Copyright (c) 2010, Oracle and/or its affiliates. All rights reserved.
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; version 2 of the License.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA */
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class THD;
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struct TABLE_LIST;
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/**
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Truncate_statement represents the TRUNCATE statement.
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*/
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class Truncate_statement : public Sql_statement
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{
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private:
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/* Set if a lock must be downgraded after truncate is done. */
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MDL_ticket *m_ticket_downgrade;
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public:
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/**
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Constructor, used to represent a ALTER TABLE statement.
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@param lex the LEX structure for this statement.
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*/
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Truncate_statement(LEX *lex)
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: Sql_statement(lex)
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{}
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virtual ~Truncate_statement()
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{}
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/**
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Execute a TRUNCATE statement at runtime.
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@param thd the current thread.
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@return false on success.
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*/
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bool execute(THD *thd);
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protected:
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/** Handle locking a base table for truncate. */
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bool lock_table(THD *, TABLE_LIST *, bool *);
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/** Truncate table via the handler method. */
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int handler_truncate(THD *, TABLE_LIST *, bool);
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/**
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Optimized delete of all rows by doing a full regenerate of the table.
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Depending on the storage engine, it can be accomplished through a
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drop and recreate or via the handler truncate method.
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*/
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bool truncate_table(THD *, TABLE_LIST *);
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};
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#endif
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