FIX: Cardinality estimates for literals that are outside the histogram range are very low

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Article ID: 833406 - View products that this article applies to.
Bug #: 470474 (SHILOH_BUGS)
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SYMPTOMS

The Microsoft SQL Server query optimizer may underestimate the cardinality of a predicate of the form column = constant when all the following conditions are true:
  • Statistics exist for the specified column.
  • The constant that is specified in the predicate is outside the range of the histogram. To determine whether the constant is outside the range, run the DBCC SHOW_STATISTICS statement, and then note when the value of the constant is less than the first RANGE_HI_KEY entry or greater than the last entry of the output.
  • The rowmodctr value for the index is not zero. This value indicates that inserts, updates, or deletes have occurred since the statistics were last updated, and a significant part of the modified rows have statistics values that are outside the current histogram boundaries.
When this problem occurs, SQL Server may not generate an optimal execution plan for your query, and poor performance may result.

These symptoms are fairly common for tables that have parent-child relationships when all the following conditions are true:
  • The parent table has a primary key on a column that is an increasing key value, such as an identity column or a datetime value that reflects the insert time.
  • The foreign key in the child table references the primary key column from the parent table.

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 file attributes) 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
   ------------------------------------------------------------------------
   31-May-2003  18:45  2000.80.818.0      78,400  Console.exe      
   28-Oct-2003  04:21  2000.80.873.0     315,968  Custtask.dll     
   02-Oct-2003  20:59  2000.80.867.0      33,340  Dbmslpcn.dll     
   25-Apr-2003  02:12                    786,432  Distmdl.ldf
   25-Apr-2003  02:12                  2,359,296  Distmdl.mdf
   30-Jan-2003  01:55                        180  Drop_repl_hotfix.sql
   12-Sep-2003  03:26  2000.80.859.0   1,905,216  Dtspkg.dll       
   26-Aug-2003  20:16  2000.80.854.0     528,960  Dtspump.dll      
   23-Jun-2003  22:40  2000.80.837.0   1,557,052  Dtsui.dll        
   23-Jun-2003  22:40  2000.80.837.0     639,552  Dtswiz.dll       
   24-Apr-2003  02:51                    747,927  Instdist.sql
   03-May-2003  01:56                      1,581  Inst_repl_hotfix.sql
   08-Feb-2003  06:40  2000.80.765.0      90,692  Msgprox.dll      
   01-Apr-2003  02:07                      1,873  Odsole.sql
   05-Apr-2003  01:46  2000.80.800.0      62,024  Odsole70.dll     
   07-May-2003  20:41  2000.80.819.0      25,144  Opends60.dll     
   02-Apr-2003  21:48  2000.80.796.0      57,904  Osql.exe         
   02-Apr-2003  23:15  2000.80.797.0     279,104  Pfutil80.dll     
   04-Aug-2003  18:17                    550,780  Procsyst.sql
   12-Sep-2003  00:37                     12,305  Qfe469315.sql
   22-May-2003  22:57                     19,195  Qfe469571.sql
   06-Sep-2003  01:36                  1,090,932  Replmerg.sql
   06-Sep-2003  07:18  2000.80.858.0     221,768  Replprov.dll     
   06-Sep-2003  07:18  2000.80.858.0     307,784  Replrec.dll      
   06-Sep-2003  00:00                  1,087,150  Replsys.sql
   13-Aug-2003  16:28                    986,603  Repltran.sql
   22-Oct-2003  00:08  2000.80.871.0      57,916  Semnt.dll        
   29-Jul-2003  20:13  2000.80.819.0     492,096  Semobj.dll       
   31-May-2003  18:27  2000.80.818.0     172,032  Semobj.rll
   05-Aug-2003  21:06                    127,884  Sp3_serv_uni.sql
   01-Jun-2003  01:01  2000.80.818.0   4,215,360  Sqldmo.dll       
   07-Apr-2003  17:44                     25,172  Sqldumper.exe    
   19-Mar-2003  18:20  2000.80.789.0      28,672  Sqlevn70.rll
   27-Sep-2003  04:42  2000.80.865.0     180,792  Sqlmap70.dll     
   03-Sep-2003  02:56  2000.80.857.0     188,992  Sqlmmc.dll       
   02-Sep-2003  23:03  2000.80.857.0     479,232  Sqlmmc.rll
   22-Oct-2003  00:08  2000.80.871.0     401,984  Sqlqry.dll       
   08-Feb-2003  06:40  2000.80.765.0      57,920  Sqlrepss.dll     
   03-Dec-2003  23:52  2000.80.891.0   7,606,353  Sqlservr.exe     
   25-Jul-2003  21:44  2000.80.845.0     590,396  Sqlsort.dll      
   08-Feb-2003  06:40  2000.80.765.0      45,644  Sqlvdi.dll       
   02-Oct-2003  20:59  2000.80.867.0      33,340  Ssmslpcn.dll     
   01-Jun-2003  01:01  2000.80.818.0      82,492  Ssnetlib.dll     
   01-Jun-2003  01:01  2000.80.818.0      25,148  Ssnmpn70.dll     
   28-Oct-2003  04:21  2000.80.873.0     123,456  Stardds.dll      
   01-Jun-2003  01:01  2000.80.818.0     158,240  Svrnetcn.dll     
   31-May-2003  18:59  2000.80.818.0      76,416  Svrnetcn.exe     
   30-Apr-2003  23:52  2000.80.816.0      45,132  Ums.dll          
   02-Jul-2003  00:19  2000.80.834.0      98,816  Xpweb70.dll      
Note Because of file dependencies, the most recent hotfix or feature that contains these files may also contain additional files.

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.

MORE INFORMATION

To explicitly enable this hotfix, you must turn on trace flag 9185. If you experience the problem that is described in the "Symptoms" section, you may also experience a similar problem with joins. Trace flag 9205 is used to enable the join-related hotfix. We recommend that you enable both of these trace flags together. For additional information about the problem with joins, click the following article number to view the article in the Microsoft Knowledge Base:
319173 FIX: Cardinality estimates are too low when value is outside histogram
For additional information, click the following article number to view the article in the Microsoft Knowledge Base:
824684 Description of the standard terminology that is used to describe Microsoft software updates

Properties

Article ID: 833406 - Last Review: May 2, 2008 - Revision: 3.1
APPLIES TO
  • Microsoft SQL Server 2000 Developer Edition
  • Microsoft SQL Server 2000 Standard Edition
  • Microsoft SQL Server 2000 Personal Edition
  • Microsoft SQL Server 2000 Enterprise Edition
  • Microsoft SQL Server 2000, Workgroup Edition
  • Microsoft SQL Server 2000 Enterprise Edition 64-bit
Keywords: 
kbhotfixserver kbqfe kbsqlserv2000presp4fix kbfix kbbug KB833406

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