我可以做些啥来加快这个 SQL 查询的速度？

Posted 2023-03-28

【中文标题】我可以做些啥来加快这个 SQL 查询的速度？

【英文标题】：What can I do to speed up this SQL Query?我可以做些什么来加快这个 SQL 查询的速度？

【发布时间】：2012-10-30 14:44:44

【问题描述】：

这里有一些细节，我尝试制作一个 SQLFiddle，但我的变量一直出错。这适用于 Sql Server 2008。我的问题是，我怎样才能使我的查询更快？我知道我在这里做错了很多事情（重复的嵌套查询），我希望有人来看看并帮助我将其从 30 分钟的执行时间中缩短！ :-S

查询背后的基本思想是，在游戏中我想找到所有在一段时间内没有移动 5 个单位的玩家，他们在静止不动时开火并且在停止移动前 60 分钟没有开火.

查询有效，但它是 AND NOT EXISTS 子句让事情慢下来，然后我补充说它需要 16 秒才能运行！ 16 秒仍然很长，所以任何其他改进都将不胜感激，但现在这是我自己的 POC 游戏（只是把零碎的东西放在一起），16 秒是可以接受的......

DECLARE @n INT , @DistanceLimit INT
SELECT  @n = 2 , @DistanceLimit = 5;

WITH    partitioned
          AS ( SELECT   * ,
                        CASE WHEN Distance < @DistanceLimit THEN 1
                             ELSE 0
                        END AS PartitionID
               FROM     EntityStateEvent
               WHERE    ExerciseID = '8B50D860-6C4E-11E1-8E70-0025648E65EC'
             ),
        sequenced
          AS ( SELECT   ROW_NUMBER() OVER ( PARTITION BY PlayerID ORDER BY EventTime ) AS MasterSeqID ,
                        ROW_NUMBER() OVER ( PARTITION BY PlayerID, PartitionID ORDER BY EventTime ) AS PartIDSeqID ,
                        *
               FROM     partitioned
             ),
        filter
          AS ( SELECT   MasterSeqID - PartIDSeqID AS GroupID ,
                        MIN(MasterSeqID) AS GroupFirstMastSeqID ,
                        MAX(MasterSeqID) AS GroupFinalMastSeqID ,
                        PlayerID
               FROM     sequenced
               WHERE    PartitionID = 1
               GROUP BY PlayerID ,
                        MasterSeqID - PartIDSeqID
               HAVING   COUNT(*) >= @n
             )
    SELECT
DISTINCT    ( sequenced.PlayerID ) ,
            MIN(sequenced.EventTime) AS StartTime ,
            MAX(sequenced.EventTime) AS EndTime ,
            DATEDIFF(minute, MIN(sequenced.EventTime),
                     MAX(sequenced.EventTime)) AS StaticTime ,
            Player.Designation AS 'Player'
    FROM    filter
            INNER JOIN sequenced ON sequenced.PlayerID = filter.PlayerID
                                    AND sequenced.MasterSeqID >= filter.GroupFirstMastSeqID
                                    AND sequenced.MasterSeqID <= filter.GroupFinalMastSeqID
            INNER JOIN Events ON Events.FiringPlayerID = sequenced.PlayerID 
            INNER JOIN Player ON Player.PlayerID = sequenced.PlayerID
                                 AND Player.Force = 'FR'
                                 AND NOT EXISTS ( SELECT    *
                                                  FROM      Events
                                                  WHERE     Events.FiringPlayerID = Player.PlayerID
                                                  GROUP BY  Events.FiringTime
                                                  HAVING    Events.FiringTime BETWEEN DATEADD(minute,
                                                              -60,
                                                              ( SELECT
                                                              MIN(s.EventTime)
                                                              FROM
                                                              sequenced s
                                                              WHERE
                                                              s.PlayerID = filter.PlayerID
                                                              AND s.MasterSeqID >= filter.GroupFirstMastSeqID
                                                              AND s.MasterSeqID <= filter.GroupFinalMastSeqID
                                                              ))
                                                              AND
                                                              ( SELECT
                                                              MIN(s.EventTime)
                                                              FROM
                                                              sequenced s
                                                              WHERE
                                                              s.PlayerID = filter.PlayerID
                                                              AND s.MasterSeqID >= filter.GroupFirstMastSeqID
                                                              AND s.MasterSeqID <= filter.GroupFinalMastSeqID
                                                              ) )
            INNER JOIN Player HitPlayer ON HitPlayer.PlayerID = Events.HitPlayerID
    WHERE   HitPlayer.[FORCE] = 'HO'
    GROUP BY GroupID ,
            sequenced.PlayerID ,
            Events.FiringPlayerID ,
            Events.FiringTime ,
            Player.Designation
    HAVING  DATEDIFF(minute, MIN(sequenced.EventTime),
                     MAX(sequenced.EventTime)) > 5
            AND Events.FiringTime BETWEEN MIN(sequenced.EventTime)
                                  AND     MAX(sequenced.EventTime)
    ORDER BY StartTime

【问题讨论】：

您可能会在 dba.stackexchange.com 上获得关于性能调整问题的更好答案

@RichardTheKiwi - 谢谢，我也会在那里发帖。

【参考方案1】：

我要做的第一件事是实现sequenced CTE，因为它在事物的整体架构中被使用了 4 次。

这意味着移动一些代码并使用#temp 表代替顺序 CTE。它还可以更好地工作一个数量级，因为您可以聚集 #temp 表并为 JOIN 创建有用的索引。

参见 this SQLFiddle，它表明 CTE 可以被评估多次，每次参考一次。

【讨论】：

实现它是什么意思？你有机会帮我一把吗？我还没有完全理解代码，移动很多东西可能会导致比我处理 atm 更多的错误！

感谢您的建议，将嵌套 CTE 更改为临时表将执行时间降低到更易于管理的 30 秒 :)