Question

我遇到了后续查询的麻烦，我提交给MySQL服务器。它需要25秒...（COUNT（*）＆lt; 20k）-tables - 只有600k行。但是，索引是在应该的位置创建的（也就是说：对于ON子句中的相关列）。我试图删除GROUP BY，这有点改进了案例。但是查询仍然会给出一个缓慢的响应。我发了这个帖子，因为我无法找到堆栈溢出中发现的各种情况的解决方案。有什么建议吗？

SELECT
    doctor.id as doctor_id,
    doctor.uuid as doctor_uuid,
    doctor.firstname as doctor_firstname,
    doctor.lastname as doctor_lastname,
    doctor.cloudRdvMask as doctor_cloudRdvMask,

    GROUP_CONCAT(recommendation.id SEPARATOR ' ') as recommendation_ids,
    GROUP_CONCAT(recommendation.uuid SEPARATOR ' ') as recommendation_uuids,
    GROUP_CONCAT(recommendation.disponibility SEPARATOR ' ') as recommendation_disponibilities,
    GROUP_CONCAT(recommendation.user_id SEPARATOR ' ') as recommendation_user_ids,
    GROUP_CONCAT(recommendation.user_uuid SEPARATOR ' ') as recommendation_user_uuids,

    location.id as location_id,
    location.uuid as location_uuid,
    location.lat as location_lat,
    location.lng as location_lng,

    profession.id as profession_id,
    profession.uuid as profession_uuid,
    profession.name as profession_name
FROM featured as doctor
LEFT JOIN location as location
    ON doctor.location_id = location.id
LEFT JOIN profession as profession
    ON doctor.profession_id = profession.id
LEFT JOIN 
    (
        SELECT 
            featured.id as id, 
            featured.uuid as uuid, 
            featured.doctor_id as doctor_id, 
            featured.disponibility as disponibility,

            user.id as user_id, 
            user.uuid as user_uuid
        FROM featured as featured
            LEFT JOIN user as user
                ON featured.user_id = user.id
            WHERE discr = 'recommendation'
        ) as recommendation
        ON recommendation.doctor_id = doctor.id
WHERE
    doctor.discr = 'doctor'
    AND
    doctor.state = 'Publié'
GROUP BY doctor.uuid

以下是EXPLAIN结果：

id | select_type | table      | partitions | type   | possible_keys              | key                  | key_len | ref                           | rows   | filtered | Extra       |

1 | SIMPLE      | doctor     | NULL       | ref    | discr,state                | discr                | 767     | const                         | 194653 |    50.00 | Using where |
1 | SIMPLE      | location   | NULL       | eq_ref | PRIMARY                    | PRIMARY              | 4       | doctoome.doctor.location_id   |      1 |   100.00 | NULL        |
1 | SIMPLE      | profession | NULL       | eq_ref | PRIMARY                    | PRIMARY              | 4       | doctoome.doctor.profession_id |      1 |   100.00 | NULL        |
1 | SIMPLE      | featured   | NULL       | ref    | IDX_3C1359D487F4FB17,discr | IDX_3C1359D487F4FB17 | 5       | doctoome.doctor.id            |    196 |   100.00 | Using where |
1 | SIMPLE      | user       | NULL       | eq_ref | PRIMARY                    | PRIMARY              | 4       | doctoome.featured.user_id     |      1 |   100.00 | Using index |

编辑这个链接对我有帮助，现在已经8s了。 https://www.percona.com/blog/2016/10/12/mysql-5-7-performance-tuning-immediately-after-installation/。但我仍觉得它很慢，我只是想让它以防任何人知道什么也可以改进。感谢

Answer 1

我认为删除子查询可能会有所帮助，还有一些索引：

SELECT . . . -- you need to fix the `GROUP_CONCAT()` column references
FROM featured doctor LEFT JOIN
     location location
     ON doctor.location_id = location.id LEFT JOIN
     profession profession
     ON doctor.profession_id = profession.id LEFT JOIN 
     featured featured
     ON featured.doctor_id = doctor.doctor_id LEFT JOIN
     user user
     ON featured.user_id = user.id
WHERE doctor.discr = 'doctor' AND
      doctor.state = 'Publié' AND
      featured.discr = 'recommendation'
GROUP BY doctor.uuid;

然后您需要featured(discr, state, doctor_id, location_id, profession_id)和featured(doctor_id, discr, user_id)上的索引。

非常慢的MySQL查询（Left-JOIN，GROUP BY等？）

1 个答案: