我的 select 查询非常慢，我需要了解如何改进它

Question

我有一个用于检索 table 数据的查询。当返回超过3-4行时，查询很慢，我不明白为什么。

这是我的查询：

select 
        ig.id,
        ig.username,
        ig.created,
        ig.is_completed,
        ig.user_id,
        ig.is_error,
        ig.last_appeal_process_update,
        (unix_timestamp() - ig.created) as time_running,
        ig.is_deleted,
        ap.id as appealprocessid,
        (case 
            when ap.id is null then 0
            when ap.id is not null then ap.status
        end
        ) as current_status,
        ( select count(*) from appeal_process where ig_account_id = ig.id)
        as total_appeals
        from instagram_accounts ig
        left join appeal_process ap on ig.id = ap.ig_account_id
        where 
        (ig.username like CONCAT('%',?,'%') or ig.id like CONCAT('%',?,'%') or ig.username like CONCAT('%',?,'%')) and 
        ig.user_id = ? and is_deleted = 0 and 
        (
            ap.id is null or
            ap.id = ( -- WE SELECT ONLY THE LATEST APPEAL PROCESS
                select max(id) from appeal_process tmp where tmp.ig_account_id = ig.id limit 1
            )   
        )
        order by ig.username asc
        limit ?,?

编辑

这是 EXPLAIN 查询（虽然我不知道如何阅读它） enter image description here

这是 为 instagram_accounts 显示创建 TABLE： enter image description here

这是 为 appeal_process 显示创建 TABLE： enter image description here

Answer 1

你的问题很可能是索引不足，需要对WHERE AND JOIN子句中使用的字段进行索引

为以下每个字段创建一个索引：

ig_account_id

ig.id

ig.username

is_deleted

ig.user_id

tmp.ig_account_id

Answer 2

在 instagram_accounts 上，您有特定于 user_id、is_deleted 以及 username 的标准。由于您还按用户名排序，第一个解决方法是添加索引。

CREATE INDEX user_id_deleted_username ON
             instagram_accounts(user_id, is_deleted, username);

在 appeal_process 中，您在 JOIN 和 tmp 子查询中都按 ig_account_id 进行搜索：

CREATE INDEX id_account_id ON 
             appeal_process ( ig_account_id)

在查询中，您正在提取用户最大申诉流程 ID 的状态。让 GROUP BY ig.id 简化如何获得结果，因为 MAX 和其他人是每组（为了强调而改变 CAP）：

select 
        ig.id,
        ig.username,
        ig.created,
        ig.is_completed,
        ig.user_id,
        ig.is_error,
        ig.last_appeal_process_update,
        (unix_timestamp() - ig.created) as time_running,
        ig.is_deleted,
        COALESE(MAX(ap.id),0) as appealprocessid,
        (SELECT status FROM appeal_process WHERE appeal_process.id = appealprocessid LIMIT 1) as current_status,
        COUNT(*) as total_appeals
        from instagram_accounts ig
        left join appeal_process ap on ig.id = ap.ig_account_id
        where 
        (ig.username like CONCAT('%',?,'%') or ig.id like CONCAT('%',?,'%') or ig.username like CONCAT('%',?,'%')) and 
        ig.user_id = ? and is_deleted = 0 
        GROUP BY ig.id
        order by ig.username asc
        limit ?,?

我的 select 查询非常慢，我需要了解如何改进它

My select query is very slow, I need insights on how to improve it

mysql

select

join

multi-select