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sql-statement-show-stats-locked.md

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SHOW STATS_LOCKED
An overview of the usage of SHOW STATS_LOCKED for the TiDB database.

SHOW STATS_LOCKED

SHOW STATS_LOCKED shows the tables whose statistics are locked.

Currently, the SHOW STATS_LOCKED statement returns the following columns:

Column name Description
Db_name The database name
Table_name The table name
Partition_name The partition name
Status The statistics status, such as locked

Synopsis

ShowStatsLockedStmt ::= 'SHOW' 'STATS_LOCKED' ShowLikeOrWhereOpt

ShowLikeOrWhereOpt ::= 'LIKE' SimpleExpr | 'WHERE' Expression

Examples

Create table t, and insert data into it. When the statistics of table t are not locked, the ANALYZE statement can be successfully executed.

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)

Lock the statistics of table t and execute SHOW STATS_LOCKED. The output shows that the statistics of table t have been locked.

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 compatibility

This statement is a TiDB extension to MySQL syntax.

See also