Question

我有一个查询，其中有一些连接。我在此查询中加入的每个表都有一个外键。当我运行它时，执行时间非常慢，大约23秒。主表有大约50,000行。

SELECT o.id, o.title, o.link, o.position_id, o.status, o.publish_date, o.archived_on, vos.name AS site_name, vorib.image AS ribbon, vop.picture,
             GROUP_CONCAT(DISTINCT CAST(voci.name AS CHAR)) AS cities,
             GROUP_CONCAT(DISTINCT CAST(vors.name AS CHAR)) AS regions,
             GROUP_CONCAT(DISTINCT CAST(voi.icon_id AS CHAR)) AS icons,
                 GROUP_CONCAT(DISTINCT CAST(voc.city_id AS CHAR)) AS cities_id,
             GROUP_CONCAT(DISTINCT CAST(vor.region_id AS CHAR)) AS regions_id,
             GROUP_CONCAT(DISTINCT CAST(vose.section_id AS CHAR)) AS sections,
             GROUP_CONCAT(DISTINCT CAST(vocat2.category_id AS CHAR)) AS categories,
             GROUP_CONCAT(DISTINCT CAST(vocategories.name AS CHAR)) AS categories_names,        
             (SELECT SUM(vocount.clicks) FROM vo_offers_counter AS vocount WHERE vocount.offer_id = vo.id) AS hits
        FROM vo_offers AS o 
                LEFT JOIN offers_pictures AS vop ON o.id = vop.offer_id AND vop.number = 1
                LEFT JOIN offer_sites AS vos ON o.site_id = vos.id
                LEFT JOIN offers_city AS voc ON o.id = voc.offer_id
                LEFT JOIN offers_category AS vocat ON o.id = vocat.offer_id
                LEFT JOIN offers_category AS vocat2 ON o.id = vocat2.offer_id
                LEFT JOIN offer_categories AS vocategories ON vocat2.category_id = vocategories.id
                LEFT JOIN offers_city AS voc2 ON o.id = voc2.offer_id
                LEFT JOIN offer_cities AS voci ON voc2.city_id = voci.id
                LEFT JOIN offers_region AS vor ON o.id = vor.offer_id
                LEFT JOIN offer_regions AS vors ON vor.region_id = vors.id
                LEFT JOIN offer_ribbons AS vorib ON o.ribbon_id = vorib.id
                LEFT JOIN offers_section AS vose ON o.id = vose.offer_id
                LEFT JOIN offers_icons AS voi ON o.id = voi.offer_id
                 WHERE o.id IS NOT NULL  AND o.status IN ('published','pending','xml')   
GROUP BY o.id  
ORDER BY CASE WHEN o.position_id IN('', '0') THEN ~0 ELSE 0 END asc, o.position_id asc, o.publish_microtime desc  
LIMIT 100 OFFSET 200

以下是查询的DESCRIBE：

  +----+--------------------+--------------+--------+---------------------------+---------------------------+---------+--------------------------------------+------+----------------------------------------------+
  | id | select_type        | table        | type   | possible_keys             | key                       | key_len | ref                                  | rows | Extra                                        |
  +----+--------------------+--------------+--------+---------------------------+---------------------------+---------+--------------------------------------+------+----------------------------------------------+
  |  1 | PRIMARY            | o            | range  | PRIMARY,status            | status                    | 2       | NULL                                 | 3432 | Using where; Using temporary; Using filesort |
  |  1 | PRIMARY            | vop          | ref    | offer_id                  | offer_id                  | 5       | new_vsichkioferti.v.id               |    1 |                                              |
  |  1 | PRIMARY            | vos          | eq_ref | PRIMARY                   | PRIMARY                   | 4       | new_vsichkioferti.v.site_id          |    1 |                                              |
  |  1 | PRIMARY            | voc          | ref    | offer_id                  | offer_id                  | 5       | new_vsichkioferti.v.id               |    2 | Using index                                  |
  |  1 | PRIMARY            | vocat        | ref    | vo_offers_category_ibfk_1 | vo_offers_category_ibfk_1 | 5       | new_vsichkioferti.v.id               |    1 | Using index                                  |
  |  1 | PRIMARY            | vocat2       | ref    | vo_offers_category_ibfk_1 | vo_offers_category_ibfk_1 | 5       | new_vsichkioferti.v.id               |    1 |                                              |
  |  1 | PRIMARY            | vocategories | eq_ref | PRIMARY                   | PRIMARY                   | 4       | new_vsichkioferti.vocat2.category_id |    1 | Using index                                  |
  |  1 | PRIMARY            | voc2         | ref    | offer_id                  | offer_id                  | 5       | new_vsichkioferti.v.id               |    2 |                                              |
  |  1 | PRIMARY            | voci         | eq_ref | PRIMARY                   | PRIMARY                   | 4       | new_vsichkioferti.voc2.city_id       |    1 | Using index                                  |
  |  1 | PRIMARY            | vor          | ref    | offer_id                  | offer_id                  | 5       | new_vsichkioferti.v.id               |    1 |                                              |
  |  1 | PRIMARY            | vors         | eq_ref | PRIMARY                   | PRIMARY                   | 4       | new_vsichkioferti.vor.region_id      |    1 | Using index                                  |
  |  1 | PRIMARY            | vorib        | eq_ref | PRIMARY                   | PRIMARY                   | 4       | new_vsichkioferti.v.ribbon_id        |    1 |                                              |
  |  1 | PRIMARY            | vose         | ref    | offer_id                  | offer_id                  | 5       | new_vsichkioferti.v.id               |    1 | Using index                                  |
  |  1 | PRIMARY            | voi          | ref    | offer_id                  | offer_id                  | 5       | new_vsichkioferti.v.id               |    1 | Using index                                  |
  |  2 | DEPENDENT SUBQUERY | vocount      | ref    | offer_id                  | offer_id                  | 5       | func                                 |    1 | Using where                                  |
  +----+--------------------+--------------+--------+---------------------------+---------------------------+---------+--------------------------------------+------+----------------------------------------------+
  15 rows in set

我该怎么做才能让它跑得更快？

[编辑]

问题出在这个联接中：

LEFT JOIN offers_city AS voc2 ON o.id = voc2.offer_id
LEFT JOIN offer_cities AS voci ON voc2.city_id = voci.id

主要在第一个，表offers_city是221339行但只有两列：offer_id和city_id带索引，两者都是外键

Answer 1

我看到那里的WHERE部分只按主表（vo_offers AS o）列过滤。如果情况总是如此 - 您可以尝试使用子选择来加速它。您查询的内容是 - 它确实（可能不是100％肯定）首先连接来自连接表的所有其他记录，然后执行过滤。

所以你可以尝试类似的东西：

SELECT o.id, o.title, o.link, o.position_id, o.status, o.publish_date, o.archived_on, vos.name AS site_name, vorib.image AS ribbon, vop.picture,
             GROUP_CONCAT(DISTINCT CAST(voci.name AS CHAR)) AS cities,
             GROUP_CONCAT(DISTINCT CAST(vors.name AS CHAR)) AS regions,
             GROUP_CONCAT(DISTINCT CAST(voi.icon_id AS CHAR)) AS icons,
                 GROUP_CONCAT(DISTINCT CAST(voc.city_id AS CHAR)) AS cities_id,
             GROUP_CONCAT(DISTINCT CAST(vor.region_id AS CHAR)) AS regions_id,
             GROUP_CONCAT(DISTINCT CAST(vose.section_id AS CHAR)) AS sections,
             GROUP_CONCAT(DISTINCT CAST(vocat2.category_id AS CHAR)) AS categories,
             GROUP_CONCAT(DISTINCT CAST(vocategories.name AS CHAR)) AS categories_names,        
             (SELECT SUM(vocount.clicks) FROM vo_offers_counter AS vocount WHERE vocount.offer_id = vo.id) AS hits
        FROM (SELECT * FROM vo_offers WHERE id IS NOT NULL AND status IN ('published','pending','xml')) AS o
                LEFT JOIN offers_pictures AS vop ON o.id = vop.offer_id AND vop.number = 1
                LEFT JOIN offer_sites AS vos ON o.site_id = vos.id
                LEFT JOIN offers_city AS voc ON o.id = voc.offer_id
                LEFT JOIN offers_category AS vocat ON o.id = vocat.offer_id
                LEFT JOIN offers_category AS vocat2 ON o.id = vocat2.offer_id
                LEFT JOIN offer_categories AS vocategories ON vocat2.category_id = vocategories.id
                LEFT JOIN offers_city AS voc2 ON o.id = voc2.offer_id
                LEFT JOIN offer_cities AS voci ON voc2.city_id = voci.id
                LEFT JOIN offers_region AS vor ON o.id = vor.offer_id
                LEFT JOIN offer_regions AS vors ON vor.region_id = vors.id
                LEFT JOIN offer_ribbons AS vorib ON o.ribbon_id = vorib.id
                LEFT JOIN offers_section AS vose ON o.id = vose.offer_id
                LEFT JOIN offers_icons AS voi ON o.id = voi.offer_id
GROUP BY o.id  
ORDER BY CASE WHEN o.position_id IN('', '0') THEN ~0 ELSE 0 END asc, o.position_id asc, o.publish_microtime desc  
LIMIT 100 OFFSET 200

所以在这种情况下，你首先（在子选择中）找到你真正需要的记录，然后才加入所有其他表

不确定它是否会有所帮助，但你至少可以尝试一下......

MySql查询发送数据变慢

1 个答案: