sql-statement-unlock-stats.md

title	summary
UNLOCK STATS	TiDB 数据库中 UNLOCK STATS 的使用概况。

UNLOCK STATS

UNLOCK STATS 语句用于解锁统计信息被锁定的表。

警告：

锁定统计信息目前为实验特性，不建议在生产环境中使用。

语法图

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

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

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

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

示例

参考 LOCK STATS 语句的示例来创建表 t，并锁定表 t 的统计信息。

解锁表 t 的统计信息，成功执行 ANALYZE 语句。

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)

参考 LOCK STATS 语句的示例来创建表 t，并锁定表 t 的分区 p1 的统计信息。

解锁分区 p1 的统计信息，成功执行 ANALYZE 语句。

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 兼容性

该语句是 TiDB 对 MySQL 语法的扩展。

另请参阅

• 统计信息
• LOCK STATS
• SHOW STATS_LOCKED