???????? ????????? recompilation ?????? ??????

• ????????? ?? ????? ?? EXECUTE ??? ??? ?? ??? RECOMPILE ??? ?? ????? ?????
• ?????? ?????? ?? ??????, ???????, ?? ???? ?? ?????? ???? ???????? ???????? ??? ?? ???? ?? ????????? ???? ???
• ?? ???sp_recompile???? ?????? ????????? ?? ?????? ???????? ?? ?? ????
• ?????? ????????? ?? ???????? ?? ??? ?? ???? ??????? ?? ???????????? ????????? ??? (??? ?? ?????-??????? ???????? ?? ??? ???)?
• ???????? ????? ??????? ?? ??? aged ???? ?? ??? ????? ???? ?? ??? ???

• ???????? ????????? ?????? ???????? ?? ?? ???? ?????? ??? ???? ???????? ???? ?? ???????? ????????
• ????????? interleaves ???? ???????? ???? (DDL) ?? ???? Manipulation ???? (DML) ???????? ???
• ????????? ??????? ???? ?? ??? ???????? ?? ????????? ???? ???

????? ?? ???? ????

??????? ??????

exec dbo.myProc
				

exec myProc
				

????? ?? ???? ????

Identifying and Resolving Issues

View the Profiler Data

• Group the Profiler trace by Event Class
  
  
  1. ????? ???????????? ??,???.
  2. ????? ????Data Columnstab, use the UP button to move theEvent Class, ??????? ???????????heading, withEvent Classfirst. Use the DOWN button to remove all other columns under the????heading.
  3. ????? ????,OK.
  Check the number of theSP:Recompileevents.
  
  You can expand the SP:Recompile group to see the details of the individual occurrences. The???column of the event indicates the name of the stored procedure that recompiled. If multiple procedures are causing recompiles, they are sorted by the number of occurrences. If you have a large number ofSP:Recompileevents and you are experiencing high CPU usage, focus on resolving the procedures that have the highest number of recompiles. Note the system process ID (SPID) and Start Time of theSP:Recompileevent for one instance of the particular stored procedure(s) and follow the steps below.
  
  If you do not see anySP:Recompileevents, but you are still experiencing a performance problem, see the following article in the Microsoft Knowledge Base:
  224587  (http://support.microsoft.com/kb/224587/ ) TO HOW: ???????????? SQL ????? ?? ??? ????????? ????????
• Determine the Statement That Triggered the Recompile Event
  
  
  1. ????? ???????????? ??,???.
  2. ????? ????Data Columnstab, use the DOWN button to remove all other columns under the????heading.
  3. ????? ?????????tab, remove all events exceptSP: ???????,SP:StmtStarting,SP:Recompile, ??SP: ?????. If you did not capture theSP:StmtStartingevent, you can substituteSP:StmtCompleted, but do not include both because doing so doubles the amount of information you need to look through.
  4. If you have identified a particular instance of a stored procedure recompilation to examine, you can limit the data you view to the specific SPID and time frame of the occurrence by using the????????? ?? ????? ????..
  5. ????? ????,OK.
  
  TheSP:Recompileevent will be raised directly following theSP:StmtStartedevent of the stored procedure statement that caused the recompilation. After the recompile event is finished, you will see a repeat of theSP:StmtStartedevent, indicating that the statement is executing with the newly generated plan.
  
  ????? ?????? ?? ????? ????:

  use pubs
  go
  drop procedure RecompProc 
  go
  create procedure RecompProc as
  create table #t (a int)
  select * from #t
  go
  exec RecompProc
  						

  If you execute this code in Query Analyzer and view the above events in a Profiler trace, you will see the following sequence:
  
  
  ?? ?????? ?? ??????? ?????? ?????? ?? ??????? ????

  Event Class	???
  SP: ???????	RecompProc
  SP:StmtStarting	create table #t (a int)
  SP:StmtStarting	select * from #t
  SP:Recompile	RecompProc
  SP:StmtStarting	select * from #t
  SP: ?????	RecompProc

  
  
  You can tell immediately that the statement that caused the recompilation was:
  

  select * from #t
  						

  Because it appears both before and after theSP:Recompile??????
  
  ??? ?? ???? ?????? ???? ??? ??SP:StmtCompleted?????, ????? ????SP:StmtStarting????? ?? ???,SP:Recompile????? ?? ????? ?? ??? ??? ???? ??? ???? ??????:
  
  
  ?? ?????? ?? ??????? ?????? ?????? ?? ??????? ????

  ????? ????	???
  SP: ???????	RecompProc
  SP:Recompile	RecompProc
  SP:StmtCompleted	?? ??? ???? * ?? # t
  SP: ?????	RecompProc

  
  
  ?? ?? ??? ???? ???SP:Recompile????? ???? ?? ???? ????? ??SP:StmtCompleted?? ??? ????? "?? ??? ???? * # t ??" ???, ?? recompilation ?? ????? ?? ??? ???? ????? ???? ?? ?? ?? ?? recompile ?? ??? ?? ?????? ????? ????? ?? ??, ??? ??? sense, ???? ??? ?? ???? ????? ??? ???????? ?? ??? ???SP:StmtStarting?????? ??? ?? ???? ?????? ???? ??? ??SP:StmtCompleted????? ?? ???, ??? ?? ??? ??? ?? ????? ?? ??? ??? ????SP:Recompile, ??? explained ?? ??? ????
  
  ???? ?? ??? ?? ????????? ?? ????? ???????? ????????? ?????? ???, SQL Server ????? ????? ?????? ????? ?? ?? ????????? ?? ??? ??? ????? ?? ???? ??????? recompile ????? ?? ????????? ?? ???? ????????, ?? ??? ?? ???? ?? ????????? ?? ?? ??? re-create ????????? ?? ????????? ????? ?? ???? ?? "Recompilations ???? ?? ????: ????? ???? ???????? ???? (DDL) ?? ???? Manipulation ???? (DML) ??????" ??? ??? ?? ??????? ?????? ??? recompilation ?? ???? discussed ??; ?? ?? ?? ?? ?????? ?? ????? ?? ??? ?? ???????? ??? recompilation ???? ?? ??? ?? ?? ???????? ???? illustrate ???? ?? ??? ???

?????? ?? ?????? ?? ???? recompilations

drop procedure RowModifications 
go
create procedure RowModifications as
-- assume SomeTable exists with the same definition as #t, 
-- and has over 1000 rows
create table #t (a int, b char(10))
select * from #t
insert #t select * from SomeTable
select count(*) from #t  where a = 37
go
exec RowModifications
exec RowModifications
				

• Execute the statement usingsp_executesql.
  This is the preferred method. Statements executed using thesp_executesqlstored procedure are not compiled as part of the stored procedure plan. Therefore, when executing the statement, SQL Server will be free to either use an existing plan in cache for the statement or create a new one at run time. In either case, the plan for the calling stored procedure is unaffected and does not have to be recompiled.
  
  The EXECUTE statement will have the same effect; however, it is not recommended. Using the EXECUTE statement is not as efficient as usingsp_executesqlbecause it does not allow for parameterization of the query.
  
  TheRowModificationsprocedure given above can be written to usesp_executesql???????????:
  
  

  drop procedure RowModifications2 
  go
  create procedure RowModifications2 as
  set nocount on
  -- assume SomeTable exists with the same definition as #t, 
  -- and has over 1000 rows
  create table #t (a int, b char(10))
  select * from #t
  insert #t select * from SomeTable
  exec sp_executesql N'select count(*) from #t where a = @a', 
                     N'@a int', @a =  37
  go
  exec RowModifications2
  exec RowModifications2
  						

  
  For the second execution of theRowModifications2procedure, you will see the following events in Profiler:
  
  
  ?? ?????? ?? ??????? ?????? ?????? ?? ??????? ????

  Event Class	???
  SP: ???????	RowModifications2
  SP:StmtStarting	create table #t (a int, b char(10))
  SP:StmtStarting	select * from #t
  SP:StmtStarting	insert #t select * from SomeTable
  SP:StmtStarting	exec sp_executesql N'select count(*) from #t where a = @a', N'@a int', @a = 37
  SP: ???????
  SP:StmtStarting	select count(*) from #t where a = @a
  Auto-UpdateStats	???
  SP:StmtStarting	select count(*) from #t where a = @a
  SP: ?????
  SP: ?????	RowModifications2

  
  
  Notice that there are noSP:Recompileevents for theRowModifications2procedure. There are completeSP: ??????????? ?? ???SP: ?????events for thesp_executesqlcall context, and anAuto-UpdateStatsevent for column???. However, because this call is out of the context of the stored procedure, theRowModifications2procedure does not need to be recompiled in this case.
  
  For more information on using thesp_executesqlstored procedure, see the "sp_executesql (T-SQL)" and "Using sp_executesql" topics in SQL Server Books Online.
• Use sub-procedures to execute the statements that are causing the recompilations.
  In this case, the statement may still cause a recompilation, but instead of recompiling the large calling stored procedure, it will only recompile the small sub-procedure.
• Use the KEEP PLAN option.
  Temporary tables have special rules regarding recompilations which, in some cases, can be more stringent than the default recompilation algorithm. You can use the KEEP PLAN option to relax the temporary table threshold back to the default algorithm. For more information, see the "Avoiding Recompilation by Using the KEEP PLAN Option" section of this article.

• ?????? ?? ??????? ?????? ?? ????? ???? ??, ?????? ?? ?????? ?? ?????? ???????? ?? ?????? ???????? ???????????? ???? ?? ??? ???? ???? ??? ??? ???????? ?????? ??? ???????? ???? ?????? ??? ???? ?? ????????? ????, ??????? ?????? ????? ????? ?? ?? ??, ???????? ????????? recompiled ?? ?????? ??????? ???? ???????? ??? ???? ???? ???? ??? recompilation ???????? "Avoiding Recompilation ?????? ????? ???? ?? ????? ????? ??????" ??? ????? ???? ??? ?? ?? ??? ?? ???? ?? ????
• ??????? ?? ???????????? ?? ???? executions ?? ???? ??? recompilation ???? ??? ?? ??????? ?????? # t ??? ?? recompilation ?? ?????? ??? "Recompilations ???? ?? ????: ????? ???? ???????? ???? (DDL) ?? ???? Manipulation ???? (DML) ??????" discussed ??? ?? ???? ?? ????
• ?? ??????, ???? ???? simple ??? "# t ?? count(*) ?? ??? ????" ??? ?? ????? ???? ??? ?? "?? ??? ???? * # t ??" ???? ??????? recompilations ?? ????, ?? ??? SQL ????? ???? ????? "trivial ???????" recompiling (???? ?? ?? ?? ??? ???? * ???? ?????? ??) ?????? ?? ?????? ?? ?????

????: ????? ???? ???????? ???? (DDL) ?? ???? Manipulation ???? (DML) ?????? ?? ???? recompilations

drop procedure Interleave 
go
create procedure Interleave as
-- DDL
create table t1 (a int)
-- DML
select * from t1
-- DDL
create index idx_t1 on t1(a)
-- DML
select * from t1
-- DDL
create table t2 (a int)
-- DML
select * from t2
go
exec Interleave
				

1. ????????? ???? ?? ?????? compilation ?? ????? ???????? t1 ?? t2 ????? ???? ???? ?????, ?? ???????? ?? ???????? ?????? ?? ??? ??? ????? ????? ?? ????? ?? ???????? ??? ????? ???? ???? ??????
2. ???? ??? ?? ??? ????????? ????????? ???? ??, ?? ??? ??? ???? ??? ?? ?????? t1 ????? ?? ???? ???? ??? ?? ?? ?????? t1--?? ??? ??? ????? ?? ?? ???? ??? ??? ?????, ????????? ?? recompiled ?? ????? ?? ??? ?? ??? ???? ?? ??? ?? ????? ?? ?????? ???? ?? ???? ??????????? ????? ?? ??? ?? ????? ????? t1 ?? ??????? ??? ????, ??? ?? t1 ?? ?? ??? ???? ?? ??? ??? ??? ????? ?? t2 ?? ??? ???? ?? ??? ?? ???? ??? ????? ???? ?? ???? ??????? t2 ??? ?? ????? ???? ?? ????
3. ???? ??? ?? t1 ??????????? ?? ????? ?? ??? ??? ????? ??, t1 ?? ???? ???? ?? ??? ???? ??, ?? ?? ??? ?? ????? ???? recompile ?? ??? ???????, t1 ?? ?????? ????????? ???? ??? ??????? ?? ????? ????? ?? ?? ??, ??????? ????????? ?????? ?? recompiled ???: t1 ?? ??? ???? ?? ??? ?? ?? ????? ?? ??????? ???? ?? ???? ?? t2 ??? ?? ????? ???? ??, ??????? ??? ????? t ?? ?? ??? ???? ?? ??? ????? ?? ???? ????
4. ????, ?????? t2 ????? ?? ?? ???????? ?? ??? ???? t2 ?? ??? ???????? ??? ?? ??? ??? ????? ????? ??, ??????? ????????? ?? ?? ????? ??? recompiled ???

drop procedure NoInterleave 
go
create procedure NoInterleave as
-- All DDL first
create table t1 (a int)
create index idx_t1 on t1(a)
create table t2 (a int)
-- Then DML 
select * from t1
select * from t1
select * from t2
go
exec NoInterleave 
exec NoInterleave
				

1. ????????? ???? ?? ?????? compilation ?? ????? ???????? t1 ?? t2 ????? ???? ???? ?????, ?? ???????? ?? ???????? ?????? ?? ??? ??? ????? ????? ?? ????? ?? ???????? ??? ????? ???? ???? ??????
2. ???? ??? ????????? ?? ????? ???? ?? ??? DDL ???????? ?? t1 ???????? t1 ?? t2, ??? ?? ??????????? ??? ??? ???
3. ???? ??? ??? t1 ?? ???? ????? ??? ?? ??? ????? ?? ??? ?? ??? ?? ??? ?????? ??, ??????? ????????? recompiled ??? ??? ???????? ????? ??, ??????? ??????? ??? ????? ??? ?? ??? ???? ????? ??? ????????? ?? ??? ?? ????
4. ????????? ?? ??? ??? ????? ?? ??????? ?? ????? ???? ??? ????????? ???? ??? ???????? ???????? ?? ??? ??? ???????? ???? ???, ??????? ????????? ?? ??? recompile ???? ?? ???????? ???? ???

??? ?????? ?????? ?????? ?? ???? recompilations

• ?? ??????? ?????? ?? ??? ??? ??? ????? ??? ?? ?? ???????? ?????????, ?? ?? ?????? ?? ??? ???????? ????????? ??? ???? ??, ?? ???? EXECUTE ?? ????? ???? ??? ????????? ???? ??? ?? ???????? ??? ??? ??????? ?????? ?? ??????? ?? ??? ??sp_executesql???????? ??????????
• ?? ??????? ?????? ?? ??? ??? ??? ????? syntactically ??????? ?????? ?? ??? ??? ????? ???????? ????????? ?? ???????
• ????? ????? ????? ?? ??? ???? ????? ????? ?????? ???? ??????? ?????? ???? ???
• ???? ?? ??????? ?????? ?? ??? ??? ??? ????? ?? ???? ??????? ?????? ?? ?????? ??? ??? ??? ?????? ????? ??? ???
  
  ?????? ????? ????? ???? ???????? ????????? ??? ???? ?? ??????? ???????? ?? ??? ?????? ???? ???? ????????? ????? ???? ?? ???? ???????? ????? ???? ????? ???????? ??? ?? ?? ???
• ??? ????? ??? ??? ??????? ?????? ??? ??? ?? (???? CREATE ?????? ?? ?? ??? ????... ) ??? ??? ???? ???? ???????? ?? ?????? ??? ??? ?????... ???? ?? ????

???? ????? ?????? ?? ????? ???? Recompilation avoiding ????

drop procedure useKeepPlan 
go
create procedure useKeepPlan as
create table #t (a int, b char(3))
select * from #t
-- Make greater than 6 changes to #t
insert #t values (1, 'abc')
insert #t values (2, 'abc')
insert #t values (3, 'abc')
insert #t values (4, 'abc')
insert #t values (5, 'abc')
insert #t values (6, 'abc')
insert #t values (7, 'abc')
-- Now reference #t
select count(*) from #t 
--option (KEEP PLAN)
go
exec useKeepPlan
exec useKeepPlan
				

????? ?? ???? ????

????? ?? ???? recompilations SET ??? ????????? ??? ???????? ?????????

• ANSI_DEFAULTS
• ANSI_NULLS
• ANSI_PADDING
• ANSI_WARNINGS
• CONCAT_NULL_YIELDS_NULL

Use pubs
drop procedure test_recompile
go

create procedure test_recompile as
Set ANSI_DEFAULTS OFF
Select au_lname, au_fname, au_id from authors
where au_lname like 'L%'
--Option (Keep Plan)
Go
				

+---------------------------------------------------+
| Event Class     | Text                            | 
+---------------------------------------------------+
| SP:Starting     | test_recompile                  | 
+---------------------------------------------------+
| SP:StmtStarting | Set ANSI_DEFAULTS OFF           | 
+---------------------------------------------------+
| SP:StmtStarting | select au_lname, au_fname, au_id| 
+---------------------------------------------------+
| SP:Recompile    | test_recompile                  | 
+---------------------------------------------------+
| SP:StmtStarting | select au_lname, au_fname, au_id| 
+---------------------------------------------------+
| SP:Completed    | test_recompile                  | 
+---------------------------------------------------+
				

Set ANSI_DEFAULTS OFF

exec test_recompile
				

????? ?? ???? ????

??????

????? ?? ???? ????