Question

这是我要执行的查询

DELETE FROM testmachine WHERE workdone != 0 AND timetaken < 1617215400 LIMIT 1000;

执行查询需要 50 多秒。我想提高速度。

有什么办法可以减少执行时间吗？

这是我的列架构：

id  int UN AI PK
att text
ways    varchar(100)
mediuminv   text
mediumid    varchar(45)
timetaken   int
workdone    int
in_use  tinyint UN
status  tinyint
in  text
out text

这里是索引：

Index: idx_time_taken_work_done_in_use_status

Definition:

    Type    BTREE
    Unique  No
    Visible Yes
    Columns done
        time
        in_use
        status

TIA

Answer 1

如果查询用于类似的地方：

REPEAT
    DELETE FROM testmachine WHERE workdone != 0 AND timetaken < 1617215400 LIMIT 1000;
UNTIL !ROW_COUNT() END REPEAT;

然后试试

ALTER TABLE testmachine 
    ADD COLUMN flag BOOLEAN AS (workdone != 0 AND timetaken < 1617215400) VIRTUAL,
    ADD INDEX idx_flag (flag);

REPEAT
    DELETE FROM testmachine WHERE flag LIMIT 1000;
UNTIL !ROW_COUNT() END REPEAT;

ALTER TABLE testmachine
    DROP INDEX idx_flag,
    DROP COLUMN flag;

MySql 删除优化

1 个答案: