| title | summary |
|---|---|
SHOW STATS_LOCKED |
TiDB 数据库中 SHOW STATS_LOCKED 的使用概况。 |
SHOW STATS_LOCKED 语句显示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。
ShowStatsLockedStmt ::= 'SHOW' 'STATS_LOCKED' ShowLikeOrWhereOpt
ShowLikeOrWhereOpt ::= 'LIKE' SimpleExpr | 'WHERE' Expression
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)该语句是 TiDB 对 MySQL 语法的扩展。