SHOW STATS_LOCKED

SHOW STATS_LOCKED 语句显示统计信息被锁定的表。

SHOW STATS_LOCKED - 图1

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

ShowStatsLockedStmt

SHOW STATS_LOCKED - 图2

ShowLikeOrWhereOpt

SHOW STATS_LOCKED - 图3

  1. ShowStatsLockedStmt ::= 'SHOW' 'STATS_LOCKED' ShowLikeOrWhereOpt
  3. ShowLikeOrWhereOpt ::= 'LIKE' SimpleExpr | 'WHERE' Expression

示例

创建表 t，插入一些数据，在未锁定表 t 的统计信息的情况下成功执行 ANALYZE 语句。

  1. mysql> create table t(a int, b int);
  2. Query OK, 0 rows affected (0.03 sec)
  4. mysql> insert into t values (1,2), (3,4), (5,6), (7,8);
  5. Query OK, 4 rows affected (0.00 sec)
  6. Records: 4  Duplicates: 0  Warnings: 0
  8. mysql> analyze table t;
  9. Query OK, 0 rows affected, 1 warning (0.02 sec)
  11. mysql> show warnings;
  12. +-------+------+-----------------------------------------------------------------+
  13. | Level | Code | Message                                                         |
  14. +-------+------+-----------------------------------------------------------------+
  15. | Note  | 1105 | Analyze use auto adjusted sample rate 1.000000 for table test.t |
  16. +-------+------+-----------------------------------------------------------------+
  17. 1 row in set (0.00 sec)

锁定表 t 的统计信息，执行 ANALYZE 语句，使用 SHOW STATS_LOCKED 可查看表 t 的统计信息已被锁定。warning 提示跳过对表 t 的 ANALYZE。

  1. mysql> lock stats t;
  2. Query OK, 0 rows affected (0.00 sec)
  4. mysql> show stats_locked;
  5. +---------+------------+----------------+--------+
  6. | Db_name | Table_name | Partition_name | Status |
  7. +---------+------------+----------------+--------+
  8. | test    | t          |                | locked |
  9. +---------+------------+----------------+--------+
  10. 1 row in set (0.01 sec)
  12. mysql> analyze table t;
  13. Query OK, 0 rows affected, 2 warnings (0.00 sec)
  15. mysql> show warnings;
  16. +---------+------+-----------------------------------------------------------------+
  17. | Level   | Code | Message                                                         |
  18. +---------+------+-----------------------------------------------------------------+
  19. | Note    | 1105 | Analyze use auto adjusted sample rate 1.000000 for table test.t |
  20. | Warning | 1105 | skip analyze locked table: t                                    |
  21. +---------+------+-----------------------------------------------------------------+
  22. 2 rows in set (0.00 sec)

解锁表 t 的统计信息，成功执行 ANALYZE 语句。

  1. mysql> unlock stats t;
  2. Query OK, 0 rows affected (0.01 sec)
  4. mysql> analyze table t;
  5. Query OK, 0 rows affected, 1 warning (0.03 sec)
  7. mysql> show warnings;
  8. +-------+------+-----------------------------------------------------------------+
  9. | Level | Code | Message                                                         |
  10. +-------+------+-----------------------------------------------------------------+
  11. | Note  | 1105 | Analyze use auto adjusted sample rate 1.000000 for table test.t |
  12. +-------+------+-----------------------------------------------------------------+
  13. 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