FIX: SQL Server 2000 may underestimate the cardinality of a query expression under certain circumstances (841627)


The information in this article applies to:

  • Microsoft SQL Server 2000 Developer Edition
  • Microsoft SQL Server 2000 Standard Edition
  • Microsoft SQL Server 2000 Enterprise Edition
  • Microsoft SQL Server 2000 Personal Edition
  • Microsoft SQL Server 2000 Enterprise Evaluation Edition
  • Microsoft SQL Server 2000 Workgroup Edition
  • Microsoft SQL Server 2000 Desktop Engine (MSDE)
  • Microsoft SQL Server 2000 Developer Edition 64 bit
  • Microsoft SQL Server 2000 Enterprise Edition 64-bit
Bug #: 471399 (SQL Server 8.0)
SQL Server 8.0:471399
Microsoft SQL Server 2000 fixes are distributed as one downloadable file. Because the fixes are cumulative, each new release contains all the hotfixes and all the security fixes that were included with the previous SQL Server 2000 fix release.

SYMPTOMS

When you run a Transact-SQL query, Microsoft SQL Server 2000 may underestimate the cardinality of the query expression. Therefore, the SQL Server query optimizer may not be able to generate an optimal query execution plan, and the query performance may be slow and inconsistent. This problem occurs when both of the following conditions are true:
  • The max degree of parallelism configuration option for your instance of SQL Server is set to 0 or to a number that is greater than 1.
  • The query is based on a view.

RESOLUTION

Service pack information

To resolve this problem, obtain the latest service pack for Microsoft SQL Server 2000. For more information, click the following article number to view the article in the Microsoft Knowledge Base:

290211 How to obtain the latest SQL Server 2000 service pack

Hotfix information

The English version of this hotfix has the file attributes (or later) that are listed in the following table. The dates and times for these files are listed in coordinated universal time (UTC). When you view the file information, it is converted to local time. To find the difference between UTC and local time, use the Time Zone tab in the Date and Time tool in Control Panel. 
   Date         Time   Version            Size    File name
   -------------------------------------------------------------------------------
   27-Apr-2004  05:33  2000.80.936.0     664,128  Autoplt.dll      
   27-Apr-2004  05:33  2000.80.936.0      78,400  Console.exe      
   27-Apr-2004  05:33  2000.80.936.0     315,968  Custtask.dll     
   27-Apr-2004  05:33  2000.80.936.0      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
   27-Apr-2004  05:33  2000.80.936.0   1,905,216  Dtspkg.dll       
   27-Apr-2004  05:33  2000.80.936.0     528,960  Dtspump.dll      
   27-Apr-2004  05:33  2000.80.936.0   1,557,052  Dtsui.dll        
   27-Apr-2004  05:33  2000.80.936.0     639,552  Dtswiz.dll       
   10-Oct-2003  06:18                    747,927  Instdist.sql
   10-Oct-2003  06:18                      1,581  Inst_repl_hotfix.sql
   27-Apr-2004  05:33  2000.80.936.0      82,492  Itwiz.exe        
   27-Apr-2004  05:33  2000.80.936.0      90,692  Msgprox.dll      
   27-Apr-2004  05:33  2000.80.936.0      62,024  Odsole70.dll     
   27-Apr-2004  05:34  2000.80.936.0      25,144  Opends60.dll     
   27-Apr-2004  05:33  2000.80.936.0      57,904  Osql.exe         
   27-Apr-2004  05:33  2000.80.936.0     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
   27-Apr-2004  04:24                  1,104,848  Replmerg.sql
   27-Apr-2004  05:33  2000.80.936.0     221,768  Replprov.dll     
   27-Apr-2004  05:33  2000.80.936.0     307,784  Replrec.dll      
   27-Apr-2004  04:32  2000.80.936.0     159,813  Replres.rll
   10-Oct-2003  06:18                  1,087,150  Replsys.sql
   10-Oct-2003  06:18                    986,603  Repltran.sql
   27-Apr-2004  05:33  2000.80.936.0     287,304  Rinitcom.dll     
   27-Apr-2004  05:33  2000.80.936.0      66,112  Semmap.dll       
   27-Apr-2004  05:33  2000.80.936.0      57,916  Semnt.dll        
   27-Apr-2004  05:33  2000.80.936.0     492,096  Semobj.dll       
   27-Apr-2004  05:00  2000.80.936.0     172,032  Semobj.rll
   27-Apr-2004  05:33  2000.80.936.0      53,832  Snapshot.exe     
   11-Mar-2004  14:40                    117,834  Sp3_serv_uni.sql
   27-Apr-2004  05:32  2000.80.936.0      28,672  Sqlagent.dll     
   27-Apr-2004  05:33  2000.80.936.0     311,872  Sqlagent.exe     
   27-Apr-2004  05:32  2000.80.936.0     168,001  Sqlakw32.dll     
   27-Apr-2004  05:33  2000.80.936.0      33,344  Sqlctr80.dll     
   27-Apr-2004  05:33  2000.80.936.0   4,215,360  Sqldmo.dll       
   27-Apr-2004  05:33                     25,172  Sqldumper.exe    
   27-Apr-2004  04:22  2000.80.936.0      28,672  Sqlevn70.rll
   27-Apr-2004  05:33  2000.80.936.0     180,792  Sqlmap70.dll     
   27-Apr-2004  05:33  2000.80.936.0     188,992  Sqlmmc.dll       
   27-Apr-2004  05:01  2000.80.936.0     479,232  Sqlmmc.rll
   27-Apr-2004  05:33  2000.80.936.0     401,984  Sqlqry.dll       
   27-Apr-2004  05:33  2000.80.936.0      57,920  Sqlrepss.dll     
   27-Apr-2004  05:34  2000.80.936.0   7,581,777  Sqlservr.exe     
   27-Apr-2004  05:33  2000.80.936.0     590,396  Sqlsort.dll      
   27-Apr-2004  05:33  2000.80.936.0      45,644  Sqlvdi.dll       
   27-Apr-2004  05:33  2000.80.936.0     106,588  Sqsrvres.dll     
   27-Apr-2004  05:33  2000.80.936.0      33,340  Ssmslpcn.dll     
   27-Apr-2004  05:33  2000.80.936.0      82,492  Ssnetlib.dll     
   27-Apr-2004  05:33  2000.80.936.0      25,148  Ssnmpn70.dll     
   27-Apr-2004  05:33  2000.80.936.0     123,456  Stardds.dll      
   27-Apr-2004  05:33  2000.80.936.0     158,240  Svrnetcn.dll     
   27-Apr-2004  05:33  2000.80.936.0      76,416  Svrnetcn.exe     
   27-Apr-2004  05:34  2000.80.936.0      49,228  Ums.dll          
   27-Apr-2004  05:34  2000.80.936.0      98,872  Xpweb70.dll
Note Because of file dependencies, the most recent hotfix or feature that contains these files may also contain additional files.

WORKAROUND

To work around this problem, you must rewrite the query so that the query is based directly on the tables, instead of on the view. You can also rewrite the query to include the OPTION (MAXDOP =1) query hint to override the max degree of parallelism configuration option.

STATUS

Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.

This problem was first corrected in Microsoft SQL Server 2000 Service Pack 4.

REFERENCES

For additional information about general troubleshooting steps to perform when query performance is slow, click the following article number to view the article in the Microsoft Knowledge Base:

243589 How to troubleshoot slow-running queries on SQL Server 7.0 or later

For additional information, click the following article number to view the article in the Microsoft Knowledge Base:

831302 FIX: SQL Server underestimates the cardinality of a query expression and query performance may be slow

824684 FIX: SQL Server underestimates the cardinality of a query expression and query performance may be slow

Modification Type:MinorLast Reviewed:6/1/2006
Keywords:kbQuery kbPerformance kbTSQL kbSQLServ2000preSP4fix kbfix kbbug kbHotfixServer kbQFE KB841627 kbAudDeveloper
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