查詢是通過思考sphinx生成的。我正在尋找加快此查詢的方法。它幾乎需要永遠返回結果。有什麼辦法可以優化這個嗎?加快MYSQL左連接包含100K +記錄的查詢
SELECT
SQL_NO_CACHE `meetings`.`id` * CAST(8 AS SIGNED) + 3 AS `id`,
GROUP_CONCAT(DISTINCT IFNULL(CONCAT_WS(' ', `members`.`first_name`, `members`.`last_name`), '0') SEPARATOR ' ') AS `mentor_name`,
`meetings`.`id` AS `sphinx_internal_id`,
0 AS `sphinx_deleted`,
984144037 AS `class_crc`,
`meetings`.`program_id` AS `program_id`,
UNIX_TIMESTAMP(`meetings`.`start_time`) AS `start_time`,
`meetings`.`active` AS `active`,
`meetings`.`calendar_time_available` AS `calendar_time_available`,
`meetings`.`group_id` AS `group_id`
FROM `meetings`
LEFT OUTER JOIN `member_meetings`
ON `member_meetings`.`meeting_id` = `meetings`.`id`
LEFT OUTER JOIN `members`
ON `members`.`id` = `member_meetings`.`member_id`
WHERE
`meetings`.`delta` = 0
GROUP BY
`meetings`.`id`
ORDER BY NULL
計數
select count(*) from meetings : 194685
select count(*) from member_meetings : 522309
select count(*) from members : 112016
編輯
我想通了這個問題,我把所有的合適的索引正確配置的加入
重複的索引鍵成員_meetings.meeting_id和member_meetings.member_id,原來當使用add_index方法時,在軌道ActiveRecord :: Migration中存在一個錯誤。現在我已刪除重複的索引鍵,查詢響應時間僅爲4秒
指標心中永遠的性能,此查詢與GROUP BY子句的一個問題,所以其結果不會是你所期望的;將所有非聚合列添加到組條件 – Bohemian