If you find any compatibility differences, report them via an issue on GitHub. I see a system lock for the TRUNCATE TABLE statement, and I see 'Waiting for query cache lock' for the production users. The TRUNCATE statement in TiDB is fully compatible with MySQL. In viewing the process list, it seems that the degradation corresponds to frequent TRUNCATE TABLE statements which run on the test db (to reset the db state for the next test). TRUNCATE is faster than DELETE, as it doesn't scan every record before removing it. TRUNCATE transactions can be rolled back in database engines like SQL Server and PostgreSQL, but not in MySQL and Oracle. How does TRUNCATE TABLE work Be careful using this command. Mysql> INSERT INTO t1 VALUES (1),(2),(3),(4),(5) TRUNCATE TABLE product deletes all records stored in the table product. SynopsisĮxamples mysql> CREATE TABLE t1 (a INT NOT NULL PRIMARY KEY) TRUNCATE can be thought of as semantically the same as DROP TABLE + CREATE TABLE with the previous definition.īoth TRUNCATE TABLE tableName and TRUNCATE tableName are valid syntax. The good news is that the fix itself has been implemented MariaDB 10.2.19, MySQL 8.0.23 and later.The TRUNCATE statement removes all data from the table in a non-transactional way. truncate table testResultTable Depending on your specific needs, if you need to get rid of the table correctly and then re-create it, you can do: drop table testResultTable create table testResultTable as select. Truncate is similar to delete however, it resets the autoincrement counter back to 1 (or the initial starting value. Delete will remove all the data that meets the condition if no condition is specified, it'll remove all the data in the table. If you have a large code base and don’t explicitly specify the storage engine, you can change the default storage engine to MyISAM by adjusting the following configuration option: If you want to remove all data from the table, then your syntax is correct: truncate testResultTable or. Drop will do just that.drop the table in question, unless the table is a parent to another table. You can specify ENGINE=MyISAM in your CREATE TABLE statement. One possible solution can be delete all rows before dropping a table, this will not cause a memory stall because there will be no data in memory.Īnother solution can be use of non-InnoDB storage engine for temporary tables. You can also find more details MySQL troubleshooting article. There is different workaround for this bug depending on your circumstances as you have not shared complete detail so, I am suggesting some. Description Truncate operations drop and re-create the table, which is much faster than deleting rows one by one, particularly for large tables. If your buffer pool is 1TB that can mean your entire database locks up for as long as 30 seconds. mysql> CREATE TABLE t1 (a INT NOT NULL PRIMARY KEY) Query OK, 0 rows affected. TRUNCATE TABLE es la sentencia SQL para eliminar todos los registros/filas de una tabla sin afectar al esquema y estructura de la misma. This bug can come up when you DROP or TRUNCATE a table and you have a large buffer pool, there can be server lock-up or stall of multiple seconds which makes your table unresponsive.ĭepending on the server’s CPU and memory bandwidth, the stall can be as much as 1 second per 32GB of RAM. Both TRUNCATE TABLE tableName and TRUNCATE tableName are valid syntax. TRUNCATE TABLE is used to delete the data inside a table, but not the table itself. If you require removing table data along with its physical. If you have MySQL 5.1.15 and back, you need DELETE privilege, which my answer covers.įirst of all you should use latest version of MySQL or MariaDB as in these version this bug has been fixed. The TRUNCATE statement resets the auto-increment primary key in MySQL and SQL Server databases etc. My answer performs what TRUNCATE TABLE now does. If you have MySQL 5.1.16+, TRUNCATE TABLE requires DROP privilege. This should replicate quickly except for the last statement. You could rename the table so that it is immediately available SET FOREIGN_KEY_CHECKS = 0 ĬREATE TABLE user_engagements_new LIKE user_engagements ĪLTER TABLE user_engagements RENAME user_engagements_zap ĪLTER TABLE user_engagements_new RENAME user_engagements If any uncommitted transactions are holding onto user_engagements, that could potentially hold up a TRUNCATE TABLE as well. Using TRUNCATE TABLE on an InnoDB table requires a full table lock because TRUNCATE TABLE is DDL (Data Definition Language) not DML (Data Manipulation).ĭoing DELETE FROM user_engagements will not help because MVCC info is written to the undo logs in ibdata1, and that can hold up the table from being emptied.
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