sql-statement-show-stats-locked.md

title	summary
SHOW STATS_LOCKED	TiDB 数据库中 SHOW STATS_LOCKED 的使用概况。

SHOW STATS_LOCKED

SHOW STATS_LOCKED 语句显示统计信息被锁定的表。

目前，SHOW STATS_LOCKED 语句返回以下列：

列名	说明
Db_name	数据库名
Table_name	表名
Partition_name	分区名
Status	统计信息状态，例如 locked

语法图

ShowStatsLockedStmt ::= 'SHOW' 'STATS_LOCKED' ShowLikeOrWhereOpt

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。

mysql> CREATE TABLE t(a INT, b INT);
Query OK, 0 rows affected (0.03 sec)

mysql> INSERT INTO t VALUES (1,2), (3,4), (5,6), (7,8);
Query OK, 4 rows affected (0.00 sec)
Records: 4  Duplicates: 0  Warnings: 0

mysql> ANALYZE TABLE t;
Query OK, 0 rows affected, 1 warning (0.02 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 "Row count in stats_meta is much smaller compared with the row count got by PD, use min(1, 15000/4) as the sample-rate=1" |
+-------+------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)

锁定表 t 的统计信息，执行 SHOW STATS_LOCKED 语句，显示表 t 的统计信息被锁定。

mysql> LOCK STATS t;
Query OK, 0 rows affected (0.00 sec)

mysql> SHOW STATS_LOCKED;
+---------+------------+----------------+--------+
| Db_name | Table_name | Partition_name | Status |
+---------+------------+----------------+--------+
| test    | t          |                | locked |
+---------+------------+----------------+--------+
1 row in set (0.01 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
• UNLOCK STATS