我需要添加哪些索引？

Question

我正在尝试加快此查询的速度，并且除了最后一部分之外，我拥有所需的所有索引/外键。

查看type列，我可以看到pb正在查看all记录，我需要纠正all记录。

我想知道您是否可以帮助我找出我需要的其他索引/FK，当然，如果您有任何一般性的指示，请告诉我。

询问：

  explain SELECT  
           *
        FROM `Publish` AS pb
        LEFT JOIN Positions AS p ON pb.`Position_ID` = p.`Position_ID`
        LEFT JOIN PositionDetails AS pd ON pb.PositionDetail_ID = pd.PositionDetail_ID
        LEFT JOIN Posts AS ps ON pb.`Post_ID` = ps.`Post_ID`
        
        INNER JOIN Users AS u ON pb.`User_ID` = u.`User_ID`
        
        LEFT JOIN PublishWatch AS pw ON (p.`Position_ID` = pw.`Position_ID`  OR ps.Post_ID = pw.Post_ID ) AND   1=pw.`User_ID`
        
        LEFT JOIN UserFollow AS uf ON pb.User_ID = uf.FollowUser_ID AND  1=  uf.`User_ID` 
     
        ORDER BY pb.Published desc
        limit 0,50

解释输出：

完整的原始查询（在 php 中）：

$StrategiesWhere1 = "";

if (isset($_POST["Strategies"]) && sizeof($_POST["Strategies"]) > 0) {
    $in1 = "";
    $whereIn = [];
    foreach ($_POST["Strategies"] as $i => $item) {
        $key1 = ":1id" . $i;
        $param[$key1] = $item; // collecting values into key-value array
        array_push($whereIn, $key1);
    }

    $StrategiesWhere1 = "AND p.PositionType_ID in (" . implode(",", $whereIn) . ")";
}

$sql = "SELECT  
            pb.User_ID AS USERID,

            p.*,
            p.CommentCount as PositionCommentCount,
            p.WatchCount as PositionWatchCount,

            n.Note,

            pt.Strategy,
            pt.isUndefinedRisk,

            a.Name,
            
            u.Display,
            u.AllPosts as UserAllPosts,
            u.AllPositions as UserAllPositions,
            u.AllComments as UserAllComments,
            u.isPro,
            u.isSupporter,

            ps.*,
            ps.CommentCount as PostCommentCount,
            ps.WatchCount as PostWatchCount,
            
            pb.Published,
            pb.Publish_ID,

            pw.PublishWatch_ID,
            
            pw.AllComments AS PublishWatchAllComments,

            pd.isClosing,
            pd.isOpening,
            pd.Price,

            uf.AllComments AS UserFollowAllComments,
            uf.FollowUser_ID,
            uf.UserFollow_ID
        FROM `Publish` AS pb
        LEFT JOIN Positions AS p ON pb.`Position_ID` = p.`Position_ID`
        LEFT JOIN PositionDetails AS pd ON pb.PositionDetail_ID = pd.PositionDetail_ID
        LEFT JOIN Posts AS ps ON pb.`Post_ID` = ps.`Post_ID`
        LEFT JOIN PositionTypes AS pt ON p.`PositionType_ID` = pt.`PositionType_ID`
        LEFT JOIN Accounts AS a ON p.`Account_ID` = a.`Account_ID`
        INNER JOIN Users AS u ON pb.`User_ID` = u.`User_ID`
        LEFT JOIN Notes AS n ON p.`LastestNote_ID` = n.`Note_ID`
        
        LEFT JOIN PublishWatch AS pw ON (pb.`Position_ID` = pw.`Position_ID`  OR pb.Post_ID = pw.Post_ID ) AND  :User_ID4 = pw.`User_ID` 
        
        LEFT JOIN UserFollow AS uf ON pb.User_ID = uf.FollowUser_ID AND    :User_ID5 = uf.`User_ID`
        WHERE
      
        
            (
                (
                    :Type1 in ('Both','Only Positions') 
                    AND p.`Position_ID` IS NOT NULL 
                    AND p.`Security` LIKE :Security 
                    " . $StrategiesWhere1 . "
                ) 
                OR
                (
                    p.`Position_ID` IS NULL 
                )
            )
            -- Posts Filters
            AND  
            (
                (
                    :Type2 in ('Both','Only Posts') 
                    AND ps.Post_ID IS NOT NULL 
                    AND (
                        ps.Post like :PostContains1 
                        OR ps.Subject like :PostContains2
                    )
                    OR
                    (
                        ps.Post_ID IS NULL
                    )
                )
            )
            -- User Display name
            AND
            (
                (
                    :Display1 != ''
                    AND u.Display = :Display2
                )
                OR
                (
                    :Display3 = ''
                )
            )
            -- Account
            AND
            (
                (
                    :Account1 != ''
                    AND a.Name = :Account2
                )
                OR
                (
                    :Account3 = ''
                )
            )
            -- Only Watching 
            AND
            (
                (
                    :Watching1 = 'Both'
                )
                OR
                (
                    :Watching2 = 'Only Watched'
                    AND pw.PublishWatch_ID IS NOT NULL
                )
                OR
                (
                    :Watching3 = 'Only Unwatched'
                    AND pw.PublishWatch_ID IS NULL
                )
            )
            
            -- Pro Limitations
            AND
               (
                   (
                       -- If this is pro they get everything
                       :isPro1 = 1
                   )
                   OR 
                   (
                       -- Or if this isnt me
                       u.User_ID != 1
                   )
                   OR
                   (
                       -- If this is me and its on the small account  
                       -- or a post                      
                       u.User_ID = 1
                       AND 
                       ( a.Account_ID = 1
                           OR
                       pb.Position_ID is null)
                   )
                   OR 
                   (
                       -- If this is not pro and this is my publish and it isnt the small account or post
                       -- only show closing trade
                       u.User_ID = 1
                       AND a.Account_ID != 1
                       AND p.Closed is not null
                   )
               )
        ORDER BY pb.Published desc
        limit :Offset,:Count;
        ";

使用 Thorsten 提供的密钥更新说明：

Answer 1

首先，我会将Positions和Posts的连接条件放到它们所属的ON子句中：

LEFT JOIN Positions AS p ON pb.Position_ID = p.Position_ID
                         AND :Type1 in ('Both', 'Only Positions') 
                         AND p.Security LIKE :Security 
                         " . $StrategiesWhere1 . "

LEFT JOIN Posts AS ps ON pb.Post_ID = ps.Post_ID
                      AND :Type2 in ('Both', 'Only Posts') 
                      AND 
                      (
                        ps.Post like :PostContains1 
                        OR
                        ps.Subject like :PostContains2
                      )

在我看来有点可疑的一件事是：您选择了Positions和PositionDetails ，但两者似乎并不相关。 根据表名，我希望您只需要与PositionDetails具有相同Position_ID Positions ，但可能PositionDetails没有Position_ID 。 这可能是一个问题，如果是，我不确定这是否真的是查询的问题，还是数据模型的问题。

至于表现； 这个

ORDER BY pb.Published desc
limit :Offset,:Count;

可能会很慢。 这样做是获取整个结果集（我不知道在您的情况下这是数十行、数百行还是数千行），然后对完整集进行排序以获得所需的子集。 如果您想要前 50 行或后 50 行或后 50 行，这并不重要； DBMS 将始终必须选择完整的数据集并对其进行排序以返回所需的行。

您的所有联接仅将一个表行连接到一个Publish行，但PublishWatch除外，其中同一用户可以同时查看位置和帖子，在这种情况下，您会为一个Publish行获得两个结果行，而不是只有一个。 因此，您可以请求接下来的 50 个Published日期/时间，而不是请求接下来的 50 行：

WHERE pb.Published > :last_max_published
ORDER BY pb.Published desc
limit :Count;

因此，您将始终只查看剩余的行，而不必对已经处理过的所有行进行排序。

至于索引，您可以尝试以下操作。 其中一些覆盖索引，即它们包含查询中使用的所有列。 这意味着如果 DBMS 使用这些索引，它就不必读取表。 您可以提供所有这些索引，然后检查使用了哪些索引，然后删除其他索引。

CREATE INDEX idx01 ON Users(Display, User_ID);
CREATE INDEX idx02 ON Accounts(Name, User_ID, Account_ID);
CREATE INDEX idx03 ON Positions(Position_ID, Closed);
CREATE INDEX idx04 ON PublishWatch(User_ID, Position_ID, Post_ID, PublishWatch_ID, AllComments);
CREATE INDEX idx05 ON UserFollow(User_ID, FollowUser_ID);
CREATE INDEX idx06 ON UserFollow(FollowUser_ID, User_ID);
CREATE INDEX idx07 ON Positions(Position_ID, Security);
CREATE INDEX idx08 ON Posts(Post_ID, Post, Subject);
CREATE INDEX idx09 ON Accounts(Account_ID, Name);
CREATE INDEX idx10 ON Notes(Note_ID, Note);
CREATE INDEX idx11 ON PositionTypes(PositionType_ID, isUndefinedRisk, Strategy);
CREATE INDEX idx12 ON Publish(Published);

Answer 2

首先，我建议学习如何阅读数据库平台的执行计划。 在对查询进行故障排除时，这是一个不错的起点。 执行计划通常共享哪些索引可以帮助优化查询。 但是请注意不要只添加索引，因为这可能会无意中影响其他查询的性能。

您当前查询的一些提示：

• 仅选择您在输出中需要的列 - 您有 SELECT *用于消耗资源的多个表返回。
• 使用必要的最少连接数 - 我使用的一个（不是硬性规则）是将每个查询的连接数保持为 <= 3。 这一直对我很有帮助。
• 编写可读的 SQL 以帮助代码可维护性 - 您的 WHERE 子句难以快速阅读和理解。 6 个月后，当您（或其他人）不得不再次阅读您的查询时，通过干净利落地书写，您会感谢自己。

最好的祝愿！