将NOT IN查询转换为更好的性能

Question

我正在使用MySQL 5.0，并且需要微调此查询。 谁能告诉我在此方面可以做哪些调整？

SELECT DISTINCT(alert_master_id) FROM alert_appln_header 
WHERE created_date < DATE_SUB(CURDATE(), INTERVAL (SELECT parameters FROM schedule_config WHERE schedule_name = "Purging_Config") DAY)
AND alert_master_id NOT IN (
SELECT DISTINCT(alert_master_id) FROM alert_details 
WHERE end_date IS NULL AND created_date < DATE_SUB(CURDATE(), INTERVAL (SELECT parameters FROM schedule_config WHERE schedule_name = "Purging_Config") DAY) 
UNION
SELECT DISTINCT(alert_master_id) FROM alert_sara_header 
WHERE sara_master_id IN 
(SELECT alert_sara_master_id FROM alert_sara_lines 
WHERE end_date IS NULL) AND created_date < DATE_SUB(CURDATE(), INTERVAL (SELECT parameters FROM schedule_config WHERE schedule_name = "Purging_Config") DAY)
) LIMIT 5000;

Answer 1

我要做的第一件事是将子查询重写为joins ：

SELECT      h.alert_master_id

FROM        alert_appln_header h

       JOIN schedule_config c
         ON c.schedule_name = 'Purging_Config'

  LEFT JOIN alert_details d
         ON d.alert_master_id = h.alert_master_id
        AND d.end_date IS NULL
        AND d.created_date < CURRENT_DATE - INTERVAL c.parameters DAY

  LEFT JOIN (
              alert_sara_header s
         JOIN alert_sara_lines  l
           ON l.alert_sara_master_id = s.sara_master_id
            )
         ON s.alert_master_id = h.alert_master_id
        AND s.end_date IS NULL
        AND s.created_date < CURRENT_DATE - INTERVAL c.parameters DAY

WHERE       h.created_date < CURRENT_DATE - INTERVAL c.parameters DAY
        AND d.alert_master_id IS NULL
        AND s.alert_master_id IS NULL

GROUP BY    h.alert_master_id

LIMIT       5000

如果在那之后仍然很慢，请重新检查您的索引编制策略。 我建议索引超过：

• alert_appln_header(alert_master_id,created_date)
• schedule_config(schedule_name)
• alert_details(alert_master_id,end_date,created_date)
• alert_sara_header(sara_master_id,alert_master_id,end_date,created_date)
• alert_sara_lines(alert_sara_master_id)

Answer 2

好的，这可能只是黑暗中的一枪，但我认为您在这里不需要那么多DISTINCT 。

SELECT DISTINCT(alert_master_id) FROM alert_appln_header 
WHERE created_date < DATE_SUB(CURDATE(), INTERVAL (SELECT parameters FROM schedule_config WHERE schedule_name = "Purging_Config") DAY)
AND alert_master_id NOT IN (
     -- removed distinct here --
    SELECT alert_master_id FROM alert_details 
    WHERE end_date IS NULL AND created_date < DATE_SUB(CURDATE(), INTERVAL (SELECT parameters FROM schedule_config WHERE schedule_name = "Purging_Config") DAY) 
    UNION
     -- removed distinct here --
    SELECT alert_master_id FROM alert_sara_header 
    WHERE sara_master_id IN 
        (SELECT alert_sara_master_id FROM alert_sara_lines 
        WHERE end_date IS NULL) 
    AND created_date < DATE_SUB(CURDATE(), INTERVAL (SELECT parameters FROM schedule_config WHERE schedule_name = "Purging_Config") DAY)
) LIMIT 5000;

由于使用DISTINCT的成本很高，因此请避免使用它。 在第一个WHERE子句中要检查的ids是NOT有些结果中，所以如果该结果一定是不应该的问题ids出现不止一次。