FIX: The performance of a DML operation that fires a trigger may decrease when the trigger execution plan recompiles repeatedly

• Summary
• Symptoms
• Resolution
• Hotfix information
• Prerequisites
• Restart information
• Hotfix file information
• Status
• More Information
• References

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• The issues that are fixed by this hotfix package.
• The prerequisites for installing the hotfix package.
• Whether you must restart your computer after you install the hotfix package.
• Whether the hotfix package is replaced by any other hotfix package.
• Whether you must make any registry changes.
• The files that are contained in the hotfix package.

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• You run the DML statement multiple times.
• The number of rows that are affected by the DML statement differs every time that the DML statement is run.

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Service pack information

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Hotfix information

Prerequisites

Restart information

Hotfix file information

    Date         Time   Version       Size       File name
   ------------------------------------------------------------------
   18-Jun-2004  14:14  2000.80.954.0    664,128  Autoplt.dll      
   18-Jun-2004  14:14  2000.80.954.0     78,400  Console.exe      
   18-Jun-2004  14:14  2000.80.954.0    315,968  Custtask.dll     
   18-Jun-2004  14:14  2000.80.954.0     33,340  Dbmslpcn.dll     
   08-Apr-2004  09:12                   786,432  Distmdl.ldf
   08-Apr-2004  09:12                 2,359,296  Distmdl.mdf
   10-Oct-2003  06:18                       180  Drop_repl_hotfix.sql
   18-Jun-2004  14:14  2000.80.954.0  1,905,216  Dtspkg.dll       
   18-Jun-2004  14:14  2000.80.954.0    528,960  Dtspump.dll      
   18-Jun-2004  14:14  2000.80.954.0  1,557,052  Dtsui.dll        
   18-Jun-2004  14:14  2000.80.954.0    639,552  Dtswiz.dll       
   10-Oct-2003  06:18                   747,927  Instdist.sql
   10-Oct-2003  06:18                     1,581  Inst_repl_hotfix.sql
   18-Jun-2004  14:14  2000.80.954.0    352,828  Isqlw.exe        
   18-Jun-2004  14:14  2000.80.954.0     82,492  Itwiz.exe        
   18-Jun-2004  14:14  2000.80.954.0     90,692  Msgprox.dll      
   19-May-2004  11:13  8.11.40209.0     209,408  Mssdi98.dll      
   18-Jun-2004  14:14  2000.80.954.0     62,024  Odsole70.dll     
   18-Jun-2004  14:15  2000.80.954.0     25,144  Opends60.dll     
   18-Jun-2004  14:14  2000.80.954.0     57,904  Osql.exe         
   18-Jun-2004  14:14  2000.80.954.0    279,104  Pfutil80.dll     
   10-Oct-2003  06:07                   550,780  Procsyst.sql
   08-Apr-2004  09:12                    12,305  Qfe469315.sql
   08-Apr-2004  09:12                    19,195  Qfe469571.sql
   17-Jun-2004  02:42                 1,105,167  Replmerg.sql
   18-Jun-2004  14:14  2000.80.954.0    221,768  Replprov.dll     
   18-Jun-2004  14:14  2000.80.954.0    307,784  Replrec.dll      
   16-Jun-2004  14:07  2000.80.954.0    159,813  Replres.rll
   10-Oct-2003  06:18                 1,087,150  Replsys.sql
   10-Oct-2003  06:18                   986,603  Repltran.sql
   18-Jun-2004  14:14  2000.80.954.0    287,304  Rinitcom.dll     
   18-Jun-2004  14:14  2000.80.954.0     78,416  Sdiclnt.dll      
   18-Jun-2004  14:14  2000.80.954.0     66,112  Semmap.dll       
   18-Jun-2004  14:14  2000.80.954.0     57,916  Semnt.dll        
   18-Jun-2004  14:14  2000.80.954.0    492,096  Semobj.dll       
   16-Jun-2004  14:44  2000.80.954.0    172,032  Semobj.rll
   18-Jun-2004  14:14  2000.80.954.0     53,832  Snapshot.exe     
   11-Mar-2004  14:40                   117,834  Sp3_serv_uni.sql
   18-Jun-2004  14:13  2000.80.954.0     28,672  Sqlagent.dll     
   18-Jun-2004  14:14  2000.80.954.0    311,872  Sqlagent.exe     
   18-Jun-2004  14:13  2000.80.954.0    168,001  Sqlakw32.dll     
   18-Jun-2004  14:14  2000.80.954.0     33,344  Sqlctr80.dll     
   18-Jun-2004  14:14  2000.80.954.0  4,215,360  Sqldmo.dll       
   18-Jun-2004  14:14                    25,172  Sqldumper.exe    
   16-Jun-2004  13:54  2000.80.954.0     28,672  Sqlevn70.rll
   18-Jun-2004  14:14  2000.80.954.0    180,792  Sqlmap70.dll     
   18-Jun-2004  14:14  2000.80.954.0    188,992  Sqlmmc.dll       
   16-Jun-2004  14:52  2000.80.954.0    479,232  Sqlmmc.rll
   18-Jun-2004  14:14  2000.80.954.0    401,984  Sqlqry.dll       
   18-Jun-2004  14:14  2000.80.954.0     57,920  Sqlrepss.dll     
   18-Jun-2004  14:14  2000.80.954.0  7,581,777  Sqlservr.exe     
   18-Jun-2004  14:14  2000.80.954.0    590,396  Sqlsort.dll      
   18-Jun-2004  14:14  2000.80.954.0     45,644  Sqlvdi.dll       
   18-Jun-2004  14:14  2000.80.954.0    106,588  Sqsrvres.dll     
   18-Jun-2004  14:14  2000.80.954.0     33,340  Ssmslpcn.dll     
   18-Jun-2004  14:14  2000.80.954.0     82,492  Ssnetlib.dll     
   18-Jun-2004  14:14  2000.80.954.0     25,148  Ssnmpn70.dll     
   18-Jun-2004  14:14  2000.80.954.0    123,456  Stardds.dll      
   18-Jun-2004  14:14  2000.80.954.0    158,240  Svrnetcn.dll     
   18-Jun-2004  14:14  2000.80.954.0     76,416  Svrnetcn.exe     
   18-Jun-2004  14:14  2000.80.954.0     49,228  Ums.dll          
   18-Jun-2004  14:14  2000.80.954.0     98,872  Xpweb70.dll      

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• Run the following Transact-SQL statement in SQL Query Analyzer on the instance of SQL Server:

  DBCC TRACEON (9055, -1)

• Add -T9055 to the SQL Server startup parameters.

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Steps to reproduce the behavior

1. Start SQL Query Analyzer, and then connect to an instance of SQL Server 2000.
2. Create a table and an update trigger on the table. Name the table as cache_test and name the update trigger as cache_test_update. To do this, run the following Transact-SQL statements:

   use pubs
   go
   set nocount on
   go
   if exists (select 1 from sysobjects where id = object_id('dbo.cache_test'))
   drop table dbo.cache_test
   go
   create table dbo.cache_test
   (
   id int not null,
   descr varchar(30) not null,
   rowcreateddt datetime not null default getdate(),
   rowcreatedby varchar(30) not null default right(system_user,30),
   testcolumn varchar(30) null,
   primary key (id)
   )
   go
   
   create trigger dbo.cache_test_update
   on dbo.cache_test
   for update
   as
   if exists ( select 1 from inserted where id = 98654 )
   print 'test'
   return
   go

3. Insert some records in the cache_test table, and then remove all elements from the procedure cache. To do this, run the following Transact-SQL statements:

   insert into cache_test (id, descr, testcolumn) select 1,'Descr 1','Test 1'
   insert into cache_test (id, descr, testcolumn) select 2,'Descr 2','Test 2'
   insert into cache_test (id, descr, testcolumn) select 3,'Descr 3','Test 3'
   insert into cache_test (id, descr, testcolumn) select 4,'Descr 4','Test 4'
   insert into cache_test (id, descr, testcolumn) select 5,'Descr 5','Test 5'
   insert into cache_test (id, descr, testcolumn) select 6,'Descr 6','Test 6'
   insert into cache_test (id, descr, testcolumn) select 7,'Descr 7','Test 7'
   insert into cache_test (id, descr, testcolumn) select 8,'Descr 8','Test 8'
   insert into cache_test (id, descr, testcolumn) select 9,'Descr 9','Test 9'
   insert into cache_test (id, descr, testcolumn) select 10,'Descr 10','Test 10'
   go
   
   dbcc freeproccache

4. Update a single row in the table cache_test, and then see the plan for this single row update that is in the cache. To do this, run the following Transact-SQL statements:

   update cache_test
   set testcolumn = 'testing '+cast(id as varchar)
   where id between 1 and 1
   go
   
   select SetOpts,UseCounts,* from master..SyscacheObjects where ObjId=Object_ID('cache_test_update') order by SetOpts, CacheObjType
   go

   You notice an output that is similar to the following:
   

   SetOpts UseCounts bucketid cacheobjtype     objtype  objid      dbid dbidexec uid refcounts usecounts pagesused lasttime maxexectime avgexectime lastreads lastwrites setopts langid dateformat status sqlbytes sql
   5371	1	  10394	   Compiled Plan    Trigger  1029578706	5    5	      1	  2	    1	      1	        0	 0	     0	         0	   0	      5371    0	     1	        0	34	cache_test_update
   5371	1	  10394	   Executable Plan  Trigger  1029578706	5    5	      1	  1	    1	      1	        0	 0	     0	         0	   0	      5371    0	     1	        0	34	cache_test_update
   

5. Update four rows in the cache_test table, and then see the plan for this multiple-row update that is in the cache. To do this, run the following Transact-SQL statements:

   update cache_test
   set testcolumn = 'testing '+cast(id as varchar)
   where id between 1 and 4
   go
   
   select SetOpts,UseCounts,* from master..SyscacheObjects where ObjId=Object_ID('cache_test_update') order by SetOpts, CacheObjType
   go

   You will notice an output that is similar to the following:
   

   SetOpts UseCounts bucketid cacheobjtype     objtype  objid      dbid dbidexec uid refcounts usecounts pagesused lasttime maxexectime avgexectime lastreads lastwrites setopts langid dateformat status sqlbytes sql
   4347	1	  10394	   Compiled Plan    Trigger  1029578706	5    5	      1	  2	    1	      1	        0	 0	     0	         0	   0	      4347    0	     1	        0	34	cache_test_update
   4347	1	  10394	   Executable Plan  Trigger  1029578706	5    5	      1	  1	    1	      1	        0	 0	     0	         0	   0	      4347    0	     1	        0	34	cache_test_update
   5371	1	  10394	   Compiled Plan    Trigger  1029578706	5    5	      1	  2	    1	      1	        0	 0	     0	         0	   0	      5371    0	     1	        0	34	cache_test_update
   5371	1	  10394	   Executable Plan  Trigger  1029578706	5    5	      1	  1	    1	      1 	0	 0	     0	         0	   0	      5371    0	     1	        0	34	cache_test_update
   

6. Update five rows) in the cache_test table, and then see the plan for this multiple-row update that is in the cache. To do this, run the following Transact-SQL statements:

   update cache_test
   set testcolumn = 'testing '+cast(id as varchar)
   where id between 1 and 5
   go
   
   select SetOpts,UseCounts,* from master..SyscacheObjects where ObjId=Object_ID('cache_test_update') order by SetOpts, CacheObjType
   go
   

   You notice an output that is similar to the following:
   

   SetOpts UseCounts bucketid cacheobjtype     objtype  objid      dbid dbidexec uid refcounts usecounts pagesused lasttime maxexectime avgexectime lastreads lastwrites setopts langid dateformat status sqlbytes sql
   4347	1	  10394	   Compiled Plan    Trigger  1029578706	5    5	      1	  2	    1	      1	        0	 0	     0	         0	   0	      4347    0	     1	        0	34	cache_test_update
   4347	2	  10394	   Executable Plan  Trigger  1029578706	5    5	      1	  1	    2	      1	        0	 0	     0	         0	   0	      4347    0	     1	        0	34	cache_test_update
   

   
   If you compare this output with the output in step 5, you may notice the following conditions that could lead to the decrease in performance of the trigger execution:
   • The execution plan that corresponds to the multiple row update in the output of step 5 is deleted. This behavior occurs because the execution plan that corresponds to the multiple row update is recompiled to create a new execution plan.
   • Even though the execution plan appears to have been recompiled, the usecounts column indicates that the Executable Plan has been used two times. That is not correct.
   • Additionally, the execution plan that corresponds to the single row update has been deleted from the cache.

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