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sql-statement-unlock-stats.md

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UNLOCK STATS
An overview of the usage of UNLOCK STATS for the TiDB database.

UNLOCK STATS

UNLOCK STATS is used to unlock the statistics of a table or tables.

Synopsis

UnlockStatsStmt ::=
    'UNLOCK' 'STATS' (TableNameList | TableName 'PARTITION' PartitionNameList)

TableNameList ::=
    TableName (',' TableName)*

TableName ::=
    Identifier ( '.' Identifier )?

PartitionNameList ::=
    Identifier ( ',' Identifier )*

Examples

Refer to the examples in LOCK STATS and create a table t and lock its statistics.

Unlock the statistics of table t, and ANALYZE can be successfully executed.

mysql> UNLOCK STATS t;
Query OK, 0 rows affected (0.01 sec)

mysql> ANALYZE TABLE t;
Query OK, 0 rows affected, 1 warning (0.03 sec)

mysql> SHOW WARNINGS;
+-------+------+-----------------------------------------------------------------------------------------------------------------------------------------+
| Level | Code | Message                                                                                                                                 |
+-------+------+-----------------------------------------------------------------------------------------------------------------------------------------+
| Note  | 1105 | Analyze use auto adjusted sample rate 1.000000 for table test.t, reason to use this rate is "use min(1, 110000/8) as the sample-rate=1" |
+-------+------+-----------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)

Refer to examples in LOCK STATS and create a table t and lock the statistics of its partition p1.

Unlock the statistics of partition p1, and ANALYZE can be successfully executed.

mysql> UNLOCK STATS t PARTITION p1;
Query OK, 0 rows affected (0.00 sec)

mysql> ANALYZE TABLE t PARTITION p1;
Query OK, 0 rows affected, 1 warning (0.01 sec)

mysql> SHOW WARNINGS;
+-------+------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Level | Code | Message                                                                                                                                                              |
+-------+------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Note  | 1105 | Analyze use auto adjusted sample rate 1.000000 for table test.t's partition p1, reason to use this rate is "TiDB assumes that the table is empty, use sample-rate=1" |
+-------+------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)

MySQL compatibility

This statement is a TiDB extension to MySQL syntax.

See also