LOCK STATS

LOCK STATS

LOCK STATS 语句用于锁定表或分区的统计信息，使得在锁定期间，TiDB 不会自动更新统计信息。具体行为请参见锁定统计信息的行为说明。

语法图

LockStatsStmt

TableNameList

TableName

PartitionNameList

LockStatsStmt ::=
    'LOCK' 'STATS' (TableNameList) | (TableName 'PARTITION' PartitionNameList)
TableNameList ::=
    TableName (',' TableName)*
TableName ::=
    Identifier ( '.' Identifier )?
PartitionNameList ::=
    Identifier ( ',' Identifier )*

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 ANALYZE 语句，warning 提示跳过对表 t 的 ANALYZE。

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> ANALYZE TABLE t;
Query OK, 0 rows affected, 2 warnings (0.00 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" |
| Warning | 1105 | skip analyze locked table: test.t                                                                                                       |
+---------+------+-----------------------------------------------------------------------------------------------------------------------------------------+
2 rows in set (0.00 sec)

另外，你也可以通过 LOCK STATS 语句锁定分区的统计信息。用例如下：

创建分区表 t，插入一些数据，在未锁定分区 p1 的统计信息的情况下成功执行 ANALYZE 语句。

mysql> CREATE TABLE t(a INT, b INT) PARTITION BY RANGE (a) (PARTITION p0 VALUES LESS THAN (10), PARTITION p1 VALUES LESS THAN (20), PARTITION p2 VALUES LESS THAN (30));
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, 6 warning (0.02 sec)
mysql> SHOW WARNINGS;
+---------+------+--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Level   | Code | Message                                                                                                                                                                                                                              |
+---------+------+--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Warning | 1105 | disable dynamic pruning due to t has no global stats                                                                                                                                                                                 |
| Note    | 1105 | Analyze use auto adjusted sample rate 1.000000 for table test.t's partition p0, 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" |
| Warning | 1105 | disable dynamic pruning due to t has no global stats                                                                                                                                                                                 |
| 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"                                                                 |
| Warning | 1105 | disable dynamic pruning due to t has no global stats                                                                                                                                                                                 |
| Note    | 1105 | Analyze use auto adjusted sample rate 1.000000 for table test.t's partition p2, reason to use this rate is "TiDB assumes that the table is empty, use sample-rate=1"                                                                 |
+---------+------+--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
6 rows in set (0.01 sec)

锁定分区 p1 的统计信息，执行 ANALYZE 语句，warning 提示跳过对分区 p1 的 ANALYZE。

mysql> LOCK STATS t PARTITION p1;
Query OK, 0 rows affected (0.00 sec)
mysql> SHOW STATS_LOCKED;
+---------+------------+----------------+--------+
| Db_name | Table_name | Partition_name | Status |
+---------+------------+----------------+--------+
| test    | t          | p1             | locked |
+---------+------------+----------------+--------+
1 row in set (0.00 sec)
mysql> ANALYZE TABLE t PARTITION p1;
Query OK, 0 rows affected, 2 warnings (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" |
| Warning | 1105 | skip analyze locked table: test.t partition (p1)                                                                                                                     |
+---------+------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------+
2 rows in set (0.00 sec)

解锁统计信息请参考 UNLOCK STATS。

MySQL 兼容性

该语句是 TiDB 对 MySQL 语法的扩展。

LOCK STATS

LOCK STATS

语法图

示例

MySQL 兼容性

另请参阅