第一次运行SQL Server T-SQL查询速度慢，然后快速运行

Question

我有一个非常简单的存储过程;它第一次运行缓慢，如果输入参数相同，则运行速度很快。

它返回两个表，表头正在迅速恢复，但第二个表，它作为我与表1的结果加入它得到正确的数据变得缓慢

这里是我的存储过程的代码：

SET ANSI_NULLS ON 
GO 
SET QUOTED_IDENTIFIER ON 
GO 

ALTER PROCEDURE [dbo].[PR_ReadMdgObj] 
     (@objId int, 
     @dtFrom datetime = NULL, 
     @dtTo datetime = NULL) 
AS 
BEGIN 
    SET NOCOUNT ON 

    SET TRANSACTION ISOLATION LEVEL READ UNCOMMITTED 

    DECLARE @engine_SensorSource_id INT 

    SELECT @engine_SensorSource_id = SensorSourceid 
    FROM dbo.SensorSource 
    WHERE sourcenameid = 1 
     AND objectid = @objId 

    CREATE TABLE #10msgtable 
    (
     rownum int IDENTITY (1, 1) NOT NULL, 
     MessageId bigint NOT NULL, 
     ObjectId int NOT NULL, 
     VectorAngle int NOT NULL, 
     VectorSpeed int NOT NULL, 
     Altitude int NOT NULL, 
     GpsTime datetime NOT NULL, 
     VisibleSatelites int NULL, 
     X float, Y float, 
     engine int, 
     st int 
    ); 

    CREATE CLUSTERED INDEX IDX_C_returnTable10_GpsTime 
    ON #10msgtable (GpsTime); 

    INSERT INTO #10msgtable 
     SELECT 
      [Message].messageid, [Message].objectid, 
      [Message].vectorangle, [Message].vectorspeed, 
      [Message].altitude, [Message].gpstime, 
      [Message].visiblesatelites, 
      [Message].x, [Message].y, 
      0 Engine, 0 as t 
     FROM 
      dbo.[Message] WITH (nolock) 
     WHERE 
      [Message].ObjectId = @objId 
      AND [Message].GpsTime BETWEEN @dtFrom AND @dtTo 
      -- AND m.Valid = 1 
      -- AND m.VectorSpeed < 250 

    DELETE FROM #10msgtable 
    WHERE VectorSpeed = 250; 

    SELECT * 
    FROM #10msgtable 
    ORDER BY GpsTime ASC 

    --- select 2 
    SELECT 
     MessageSensors.MessageId, 
     SensorSource.SourceNameId, 
     MessageSensors.Value 
    FROM 
     dbo.MessageSensors 
    INNER JOIN 
     #10msgtable WITH (nolock) ON MessageSensors.MessageId= #10msgtable.MessageId 
    INNER JOIN 
     dbo.SensorSource WITH (nolock) ON SensorSource.SensorSourceId = MessageSensors.SensorSourceId 
    --where MessageSensors.MessageId in (select MessageId from #10msgtable) 

    SET TRANSACTION ISOLATION LEVEL READ COMMITTED 
END 

这里是我的实际执行计划：

https://gist.github.com/aymanstar/3ed882c6330ee6252751ce9dd2f5beac

Answer 1

有你添加一些不必要的步骤。第一次运行总是很慢（正如你已经知道的那样）。 在你的脚本

1. 没有必要添加with(nolock)的原因是由@marc_s
2. 不必要的变量声明（@engine_SensorSource_id）explaned。
3. 如果您在第一次尝试中过滤掉数据，则无需执行delete。

所以修改后的脚本应该是这样的： -

SET ANSI_NULLS ON 
GO 

SET QUOTED_IDENTIFIER ON 
GO 

ALTER PROCEDURE [dbo].[PR_ReadMdgObj] (
    @objId INT 
    ,@dtFrom DATETIME = NULL 
    ,@dtTo DATETIME = NULL 
    ) 
AS 
BEGIN 
    SET NOCOUNT ON 
    SET TRANSACTION ISOLATION LEVEL READ UNCOMMITTED 

    --DECLARE @engine_SensorSource_id INT 

    --SELECT @engine_SensorSource_id = SensorSourceid 
    --FROM dbo.SensorSource 
    --WHERE sourcenameid = 1 
    -- AND objectid = @objId 

    CREATE TABLE #10msgtable (
     rownum INT IDENTITY(1, 1) NOT NULL 
     ,MessageId BIGINT NOT NULL 
     ,ObjectId INT NOT NULL 
     ,VectorAngle INT NOT NULL 
     ,VectorSpeed INT NOT NULL 
     ,Altitude INT NOT NULL 
     ,GpsTime DATETIME NOT NULL 
     ,VisibleSatelites INT NULL 
     ,X FLOAT 
     ,Y FLOAT 
     ,engine INT 
     ,st INT 
     ); 

    CREATE CLUSTERED INDEX IDX_C_returnTable10_GpsTime ON #10msgtable (
     MessageId 
     ,GpsTime 
     ); 

    INSERT INTO #10msgtable 
    SELECT [Message].messageid 
     ,[Message].objectid 
     ,[Message].vectorangle 
     ,[Message].vectorspeed 
     ,[Message].altitude 
     ,[Message].gpstime 
     ,[Message].visiblesatelites 
     ,[Message].x 
     ,[Message].y 
     ,0 Engine 
     ,0 AS t 
    FROM dbo.[Message] 
    WHERE [Message].ObjectId = @objId 
     AND [Message].GpsTime BETWEEN @dtFrom 
      AND @dtTo 
     AND VectorSpeed <> 250 

    -- AND m.Valid = 1 
    -- AND m.VectorSpeed < 250 
    --DELETE 
    --FROM #10msgtable 
    --WHERE VectorSpeed = 250; 

    SELECT * 
    FROM #10msgtable 
    ORDER BY GpsTime ASC 

    --- select 2 
    SELECT MessageSensors.MessageId 
     ,SensorSource.SourceNameId 
     ,MessageSensors.Value 
    FROM dbo.MessageSensors 
    INNER JOIN #10msgtable ON MessageSensors.MessageId = #10msgtable.MessageId 
    INNER JOIN dbo.SensorSource ON SensorSource.SensorSourceId = MessageSensors.SensorSourceId 

    --where MessageSensors.MessageId in (select MessageId from #10msgtable) 
    SET TRANSACTION ISOLATION LEVEL READ COMMITTED 
END