MAX导致数据库超时

需求：获取指定用户下某个邮箱最近一次发送时间

场景：

CREATE_TIME，

USER_ID

已经添加索引，

ADDRESS是text字段无法添加索引。

原语句：(max导致全表扫描！！！)

SELECT
    MAX(CREATE_TIME) AS MAX0
FROM
    t_mail_send_extend
WHERE
    USER_ID = '03515d6956c0434c86175835b9fae0bf'
AND LOCATE(
    'sebastian.sandoli@ladespensa.es',
    ADDRESS
)
AND STATUS = 1

 

改进：

SELECT
    CREATE_TIME
FROM
    t_mail_send_extend
WHERE
    USER_ID = '03515d6956c0434c86175835b9fae0bf'
 AND LOCATE(
     'sebastian.sandoli@ladespensa.es',
     ADDRESS
 )
AND STATUS = 1 ORDER BY CREATE_TIME DESC LIMIT 1