Sql 使用cte ROW_NUMBER（）提高性能

我在下面的脚本中遇到了性能问题

开始时，脚本大约运行几秒钟

现在，它需要运行大约3分钟

我认为最主要的原因是

TransactionSendQueue

表，它目前有300多万行。在“ctetran”中，我需要找出最新的记录并与temp表进行比较

我尝试添加不同的索引，但它不能改善它甚至更慢。关于如何提高绩效的任何建议

WITH ctetran AS --the lastest transaction
(
    SELECT 
        Tran_ID, 
        Field2, 
        Field3, 
        Field4, 
        Field5, 
        Field6, 
        Field7, 
        Field8, 
        Field9, 
        ROW_NUMBER() OVER (PARTITION BY Tran_ID
                           ORDER BY LastUpdate DESC) AS rn
    FROM 
        TransactionSendQueue
    WHERE 
        STATUS = '1'
)  --where 1 mean complete
UPDATE temp
SET STATUS = CASE
                WHEN temp.f2 = cte.Field2
                     AND temp.f3 = cte.Field3
                     AND temp.f4 = cte.Field4
                     AND temp.f5 = cte.Field5
                     AND temp.f6 = cte.Field6
                     AND temp.f7 = cte.Field7
                     AND temp.f8 = cte.Field8
                     AND temp.f9 = cte.Field9
                   THEN '2' -- where 2 mean skip
                ELSE '3' --where 3 mean ready to execute
             END
FROM #TempTran temp
INNER JOIN ctetran cte ON temp.Tran_ID = cte.Tran_ID
                       AND cte.rn = 1;

表格设计：

CREATE TABLE [dbo].[TransactionSendQueue]
(
    [Batch_ID]   [CHAR](20) NOT NULL, 
    [Tran_ID]    [VARCHAR](20) NOT NULL,  
    [Field2]     [VARBINARY](100) NULL, 
    [Field3]     [VARBINARY](100) NULL, 
    [Field4]     [VARBINARY](100) NULL, 
    [Field5]     [VARBINARY](100) NULL, 
    [Field6]     [VARBINARY](100) NULL, 
    [Field7]     [VARBINARY](100) NULL, 
    [Field8]     [VARBINARY](100) NULL, 
    [Field9]     [VARBINARY](100) NULL, 
    [LastUpdate] [DATETIME] NOT NULL, 
    [STATUS]     [INTEGER] NOT NULL,

    CONSTRAINT [PK_TransactionSendQueue] 
        PRIMARY KEY CLUSTERED([Batch_ID], [Tran_ID])
);

---

使用多个步骤执行SQL查询时，一个核心原则是：尽早消除尽可能多的数据。当您只需要每个事务ID的最新事务时，您的CTE从TransactionSendQueue加载所有行。处理的数据越多，加载的数据写入磁盘的风险越高，这对性能极为不利。写入磁盘的数据越多，影响就越严重。你可以查看你的执行计划，看看是否是这样，但我认为这可能是考虑到执行时间

CTE每行只能返回一行，这些行可能会在#tentran表中更新。您可以使用附加的CTE首先检索最新的更新，然后在ctetran中使用该信息来减少在update语句中搜索的数据量（行）

WITH LatestTran AS --the lastest transaction
(
    SELECT 
        Tran_ID, 
        MAX(LastUpdate) AS LastUpdate
    FROM 
        TransactionSendQueue
    WHERE 
        STATUS = '1' --where 1 mean complete
    GROUP BY
        Tran_ID
), ctetran AS
(
    SELECT 
        Tran_ID, 
        Field2, 
        Field3, 
        Field4, 
        Field5, 
        Field6, 
        Field7, 
        Field8, 
        Field9
    FROM 
        TransactionSendQueue TSQ
    INNER JOIN LatestTran LT ON 
        TSQ.Tran_ID = LT.Tran_ID AND 
        TSQ.LastUpdate = LT.LastUpdate
)


UPDATE temp
SET STATUS = CASE
                WHEN temp.f2 = cte.Field2
                     AND temp.f3 = cte.Field3
                     AND temp.f4 = cte.Field4
                     AND temp.f5 = cte.Field5
                     AND temp.f6 = cte.Field6
                     AND temp.f7 = cte.Field7
                     AND temp.f8 = cte.Field8
                     AND temp.f9 = cte.Field9
                   THEN '2' -- where 2 mean skip
                ELSE '3' --where 3 mean ready to execute
             END
FROM #TempTran temp
INNER JOIN ctetran cte ON temp.Tran_ID = cte.Tran_ID

这将有多大的性能提升取决于每个Tran\u ID有多少批处理ID，越多性能提升越大

如果查询仍然运行缓慢，您还可以研究在TransactionSendQueue表中使用LastUpdate列的索引，因为查询现在在join语句中使用该索引

WITH LatestTran AS --the lastest transaction
(
    SELECT 
        Tran_ID, 
        MAX(LastUpdate) AS LastUpdate
    FROM 
        TransactionSendQueue
    WHERE 
        STATUS = '1' --where 1 mean complete
    GROUP BY
        Tran_ID
), ctetran AS
(
    SELECT 
        Tran_ID, 
        Field2, 
        Field3, 
        Field4, 
        Field5, 
        Field6, 
        Field7, 
        Field8, 
        Field9
    FROM 
        TransactionSendQueue TSQ
    INNER JOIN LatestTran LT ON 
        TSQ.Tran_ID = LT.Tran_ID AND 
        TSQ.LastUpdate = LT.LastUpdate
)


UPDATE temp
SET STATUS = CASE
                WHEN temp.f2 = cte.Field2
                     AND temp.f3 = cte.Field3
                     AND temp.f4 = cte.Field4
                     AND temp.f5 = cte.Field5
                     AND temp.f6 = cte.Field6
                     AND temp.f7 = cte.Field7
                     AND temp.f8 = cte.Field8
                     AND temp.f9 = cte.Field9
                   THEN '2' -- where 2 mean skip
                ELSE '3' --where 3 mean ready to execute
             END
FROM #TempTran temp
INNER JOIN ctetran cte ON temp.Tran_ID = cte.Tran_ID

---

请告诉我查询时间减少了多少，我很想知道。

对于性能相关的问题，我们需要使用“粘贴计划”查看执行计划。使用CTE尝试的简单方法是将其具体化到临时表中。因此，将您的cte查询结果放入临时表中，然后对cte结果执行您通常执行的任何操作。这通常可以解决cte性能问题。不过基本的cte查询仍然很慢，那么我们需要执行计划。@DaleK谢谢。执行计划很难共享。我正在尝试将其转换为临时表并再次测试。谢谢我说的使用“粘贴计划”-它正是为了这个目的。请添加索引的定义，以及临时表的定义，也共享查询计划