ANALYZE TABLE

ANALYZE TABLE 语句用于更新 TiDB 在表和索引上留下的统计信息。执行大批量更新或导入记录后,或查询执行计划不是最佳时,建议运行 ANALYZE TABLE

当 TiDB 逐渐发现这些统计数据与预估不一致时,也会自动更新其统计数据。

语法图

AnalyzeTableStmt
ANALYZETABLETableNameListTableNamePARTITIONPartitionNameListINDEXIndexNameListINCREMENTALTABLETableNamePARTITIONPartitionNameListINDEXIndexNameListAnalyzeOptionListOpt
TableNameList
TableName,
TableName
Identifier.Identifier

示例

mysql> CREATE TABLE t1 (id INT NOT NULL PRIMARY KEY AUTO_INCREMENT, c1 INT NOT NULL); Query OK, 0 rows affected (0.11 sec) mysql> INSERT INTO t1 (c1) VALUES (1),(2),(3),(4),(5); Query OK, 5 rows affected (0.03 sec) Records: 5 Duplicates: 0 Warnings: 0 mysql> ALTER TABLE t1 ADD INDEX (c1); Query OK, 0 rows affected (0.30 sec) mysql> EXPLAIN SELECT * FROM t1 WHERE c1 = 3; +-------------------+-------+------+-----------------------------------------------------------------+ | id | count | task | operator info | +-------------------+-------+------+-----------------------------------------------------------------+ | IndexReader_6 | 10.00 | root | index:IndexScan_5 | | └─IndexScan_5 | 10.00 | cop | table:t1, index:c1, range:[3,3], keep order:false, stats:pseudo | +-------------------+-------+------+-----------------------------------------------------------------+ 2 rows in set (0.00 sec) mysql> analyze table t1; Query OK, 0 rows affected (0.13 sec) mysql> EXPLAIN SELECT * FROM t1 WHERE c1 = 3; +-------------------+-------+------+---------------------------------------------------+ | id | count | task | operator info | +-------------------+-------+------+---------------------------------------------------+ | IndexReader_6 | 1.00 | root | index:IndexScan_5 | | └─IndexScan_5 | 1.00 | cop | table:t1, index:c1, range:[3,3], keep order:false | +-------------------+-------+------+---------------------------------------------------+ 2 rows in set (0.00 sec)

MySQL 兼容性

ANALYZE TABLE 在语法上与 MySQL 类似。但 ANALYZE TABLE 在 TiDB 上执行所需时间可能长得多,因为它的内部运行方式不同。

另请参阅

下载 PDF
产品
TiDB
TiDB Cloud
© 2024 PingCAP. All Rights Reserved.
Privacy Policy.