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sql-statement-commit.md

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COMMIT | TiDB SQL Statement Reference
An overview of the usage of COMMIT for the TiDB database.
/docs/dev/sql-statements/sql-statement-commit/
/docs/dev/reference/sql/statements/commit/

COMMIT

This statement commits a transaction inside of the TIDB server.

In the absence of a BEGIN or START TRANSACTION statement, the default behavior of TiDB is that every statement will be its own transaction and autocommit. This behavior ensures MySQL compatibility.

Synopsis

CommitStmt ::=
    'COMMIT' CompletionTypeWithinTransaction?

CompletionTypeWithinTransaction ::=
    'AND' ( 'CHAIN' ( 'NO' 'RELEASE' )? | 'NO' 'CHAIN' ( 'NO'? 'RELEASE' )? )
|   'NO'? 'RELEASE'

Examples

mysql> CREATE TABLE t1 (a int NOT NULL PRIMARY KEY);
Query OK, 0 rows affected (0.12 sec)

mysql> START TRANSACTION;
Query OK, 0 rows affected (0.00 sec)

mysql> INSERT INTO t1 VALUES (1);
Query OK, 1 row affected (0.00 sec)

mysql> COMMIT;
Query OK, 0 rows affected (0.01 sec)

MySQL compatibility

  • By default, TiDB 3.0.8 and later versions use Pessimistic Locking. When using Optimistic Locking, it is important to consider that a COMMIT statement might fail because rows have been modified by another transaction.
  • When Optimistic Locking is enabled, UNIQUE and PRIMARY KEY constraint checks are deferred until statement commit. This results in additional situations where a a COMMIT statement might fail. This behavior can be changed by setting tidb_constraint_check_in_place=TRUE.
  • TiDB parses but ignores the syntax ROLLBACK AND [NO] RELEASE. This functionality is used in MySQL to disconnect the client session immediately after committing the transaction. In TiDB, it is recommended to instead use the mysql_close() functionality of your client driver.
  • TiDB parses but ignores the syntax ROLLBACK AND [NO] CHAIN. This functionality is used in MySQL to immediately start a new transaction with the same isolation level while the current transaction is being committed. In TiDB, it is recommended to instead start a new transaction.

See also