是否可以在SQL Server中优化ShowPlan XML

Question

我有一个相当复杂的查询，一旦SQL server建立了查询计划(令人满意)，它只需不到一秒钟的时间就可以运行。但是，根据分析器，查询第一次运行事件ShowPlanXML大约需要14秒(不能令人满意)。

有没有办法优化ShowPlanXML，让它在第一次运行时更快地完成？

或者我要创建一个计划指南？

这里的信息是SQL查询(由NHibernate生成)：

SELECT top 20 this_.UserId as UserId55_0_, this_.User_Version as User2_55_0_, this_.User_ApplicationId as User3_55_0_, this_.User_DeletedOn as User4_55_0_, this_.User_CreatedOn as User5_55_0_, this_.User_ModifiedOn as User6_55_0_, this_.User_CreatedById as User7_55_0_, this_.User_CreatedByName as User8_55_0_, this_.User_ModifiedById as User9_55_0_, this_.User_ModifiedByName as User10_55_0_, this_.User_Name as User11_55_0_, this_.User_ExternalId as User12_55_0_, this_.User_DynamicFields as User13_55_0_, 
this_.User_FirstName as User14_55_0_, this_.User_LastName as User15_55_0_, this_.User_Prefix as User16_55_0_, this_.User_Gender as User17_55_0_, this_.User_Language as 
User18_55_0_, this_.User_Code as User19_55_0_, this_.User_Nationality as User20_55_0_, this_.User_FirstLanguage as User21_55_0_, this_.User_DrivingLicence as User22_55_0_, 
this_.User_Category as User23_55_0_, this_.User_UserStatus as User24_55_0_, this_.User_UserType as User25_55_0_, this_.User_WorkPhone as User26_55_0_, this_.User_MobilePhone as 
User27_55_0_, this_.User_Fax as User28_55_0_, this_.User_Mail as User29_55_0_, this_.User_Login as User30_55_0_, this_.User_Password as User31_55_0_, this_.User_BornOn as 
User32_55_0_, this_.User_StartedOn as User33_55_0_, this_.User_FinishedOn as User34_55_0_, this_.User_Address as User35_55_0_, this_.User_PostalCode as User36_55_0_, 
this_.User_City as User37_55_0_, this_.User_Country as User38_55_0_, this_.User_PositionTitle as User39_55_0_, this_.User_Comments as User40_55_0_, this_.User_OptionalField1 as 
User41_55_0_, this_.User_OptionalField2 as User42_55_0_, this_.User_OptionalField3 as User43_55_0_, this_.User_PasswordConsecutiveFailedAttempts as User44_55_0_, 
this_.User_PasswordModificationDate as User45_55_0_, this_.User_WrongPasswordAttemptDate as User46_55_0_, this_.User_PictureUrl as User47_55_0_, this_.User_PasswordModificationStatus as User48_55_0_, this_.User_SecretQuestionConsecutiveFailedAttempts as User49_55_0_, this_.User_PlatformMailTransfer as User50_55_0_, this_.User_TimeZoneId as User51_55_0_, this_.User_ConnectionState as User52_55_0_, this_.User_LastConnectionId as User53_55_0_, this_.User_TotalPercentRealized as User54_55_0_
FROM Dir_User this_ 
WHERE this_.UserId in (
      SELECT distinct this_0_.UserId as y0_ 
      FROM Dir_User this_0_ inner join Dir_UserDynamicGroup dynamicgro3_ on this_0_.UserId=dynamicgro3_.UsDy_UserId 
      inner join Dir_Group dynamicgro1_ on dynamicgro3_.UsDy_DynamicGroupId=dynamicgro1_.GroupId 
      WHERE dynamicgro1_.GroupId = (51904517) 
      and this_0_.User_ApplicationId = 65536 
      and this_0_.User_DeletedOn is null 
      and this_0_.UserId in (
            SELECT distinct this_0_0_.TargetUserId as y0_ 
            FROM Dir_UserGroupMember this_0_0_ 
            WHERE this_0_0_.OwnerUserId = 7341195 
            and ( (this_0_0_.Scope & 139280) != 0  or ( (this_0_0_.Scope & 139280) != 0  
            and this_0_0_.GroupId = this_0_0_.SubGroupId)))) 
            ORDER BY this_.User_Name asc

Answer 1

show-plan事件可能会对SQL Server的性能产生重大影响(请参见sqlserver.query_post_execution_showplan Performance Impact)。如果您希望获得编译存储过程所用时间的准确表示，则应使用另一种方法。

您应该能够通过直接查看计划缓存来确定计划编译所用的时间，请参见Identifying High Compile Time Statements from the Plan Cache。

不幸的是，除了简单地降低查询的复杂性之外，我不知道有多少方法可以减少SQL Server查询的编译时间。尝试通过计划缓存降低计划编译所需的频率是提高性能的标准方法。