FIX: The SQL Server 2005 query optimizer may incorrectly estimate the cardinality for a query that has a predicate that contains an index union alternative

Article ID: 920347 - View products that this article applies to.
Bug #: 438282 (SQLBUDT)
Bug #: 449130 (SQLBUDT)
Bug #: 715 (SQL Hotfix)
Bug #: 637 (SQL Hotfix)
Microsoft distributes Microsoft SQL Server 2005 fixes 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 2005 fix release.
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SUMMARY

This article describes the following about this hotfix release:
  • The issues that are fixed by this hotfix package
  • The prerequisites for installing the hotfix package
  • Information about whether you must restart the computer after you install the hotfix package
  • Information about whether the hotfix package is replaced by any other hotfix package
  • Information about whether you must make any registry changes
  • The files that are contained in the hotfix package
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SYMPTOMS

Consider the following scenario:
  • The SQL Server 2005 query optimizer evaluates a query that has a predicate.
  • The query predicate contains one alternative that is an index union.
For example, the following query is a query predicate that contains one alternative that is an index union:
select * from table where (c1 <Comparison operator> value1 OR c1 <Comparison operator> value2) and c2 <Comparison operator> value3)
In this scenario, the query optimizer may incorrectly estimate the cardinality as lower than the actual cardinality. When this problem occurs, the estimated cost of the query also becomes lower than the actual cost. When the estimated cost of the query is lower than the actual cost, the SQL Server 2005 query optimizer may use this query instead of a more efficient query.
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CAUSE

This problem occurs because of a bug in the SQL Server index strategy code.
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RESOLUTION

A supported hotfix is available from Microsoft. However, this hotfix is intended to correct only the problem that is described in this article. Apply this hotfix only to systems that are experiencing this specific problem. This hotfix might receive additional testing. Therefore, if you are not severely affected by this problem, we recommend that you wait for the next software update that contains this hotfix.

If the hotfix is available for download, there is a "Hotfix download available" section at the top of this Knowledge Base article. If this section does not appear, contact Microsoft Customer Service and Support to obtain the hotfix.

Note If additional issues occur or if any troubleshooting is required, you might have to create a separate service request. The usual support costs will apply to additional support questions and issues that do not qualify for this specific hotfix. For a complete list of Microsoft Customer Service and Support telephone numbers or to create a separate service request, visit the following Microsoft Web site:
http://support.microsoft.com/contactus/?ws=support
(http://support.microsoft.com/contactus/?ws=support)
Note The "Hotfix download available" form displays the languages for which the hotfix is available. If you do not see your language, it is because a hotfix is not available for that language.

Prerequisites

You must have Microsoft SQL Server 2005 Service Pack 1 (SP1) installed to apply this hotfix.

For more information about how to obtain SQL Server 2005 Service Pack 1, click the following article number to view the article in the Microsoft Knowledge Base:
913089
(http://support.microsoft.com/kb/913089/ )
How to obtain the latest service pack for SQL Server 2005

Restart information

You do not have to restart the computer after you apply this hotfix.

Registry information

You do not have to change the registry.

Hotfix replacement information

This hotfix does not replace any other hotfixes.

Hotfix file information

This hotfix contains only those files that are required to correct the issues that this article lists. This hotfix may not contain of all the files that you must have to fully update a product to the latest build.

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 item in Control Panel.
SQL Server 2005 hotfix, 32-bit
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File nameFile versionFile sizeDateTimePlatform
Microsoft.sqlserver.sqlenum9.0.2164.0908,06415-Jun-200603:32Not Applicable
Ms.ss.mgdsqldumper.dll2005.90.2164.075,55215-Jun-200603:29Not Applicable
Msgprox.dll2005.90.2164.0197,92015-Jun-200603:29Not Applicable
Replprov.dll2005.90.2164.0547,61615-Jun-200603:31Not Applicable
Replrec.dll2005.90.2164.0782,11215-Jun-200603:32Not Applicable
Sbmsmdlocal.dll9.0.2164.015,661,85615-Jun-200603:33Not Applicable
Sqlaccess.dll2005.90.2164.0347,93615-Jun-200603:31Not Applicable
Sqlservr.exe2005.90.2164.028,950,87215-Jun-200603:33Not Applicable
SQL Server 2005 hotfix, 64-bit
Collapse this tableExpand this table
File nameFile versionFile sizeDateTimePlatform
Microsoft.sqlserver.sqlenum9.0.2164.0875,29615-Jun-200604:12Not Applicable
Ms.ss.mgdsqldumper.dll2005.90.2164.075,55215-Jun-200603:29Not Applicable
Ms.ss.mgdsqldumper.dll2005.90.2164.091,42415-Jun-200604:10Not Applicable
Msgprox.dll2005.90.2164.0259,36015-Jun-200604:10Not Applicable
Replprov.dll2005.90.2164.0745,24815-Jun-200604:12Not Applicable
Replrec.dll2005.90.2164.01,008,41615-Jun-200604:12Not Applicable
Sbmsmdlocal.dll9.0.2164.015,661,85615-Jun-200603:33Not Applicable
Sqlaccess.dll2005.90.2164.0355,10415-Jun-200604:11Not Applicable
Sqlservr.exe2005.90.2164.039,251,23215-Jun-200604:13Not Applicable
SQL Server 2005 hotfix, 64-bit for Itanium processors
Collapse this tableExpand this table
File nameFile versionFile sizeDateTimePlatform
Microsoft.sqlserver.sqlenum9.0.2164.0875,29615-Jun-200603:29Not Applicable
Ms.ss.mgdsqldumper.dll2005.90.2164.075,55215-Jun-200603:29Not Applicable
Ms.ss.mgdsqldumper.dll2005.90.2164.0163,10415-Jun-200603:29Not Applicable
Msgprox.dll2005.90.2164.0542,49615-Jun-200603:28Not Applicable
Replprov.dll2005.90.2164.01,617,18415-Jun-200603:29Not Applicable
Replrec.dll2005.90.2164.02,141,47215-Jun-200603:29Not Applicable
Sbmsmdlocal.dll9.0.2164.048,733,98415-Jun-200603:30Not Applicable
Sqlaccess.dll2005.90.2164.0349,47215-Jun-200603:28Not Applicable
Sqlservr.exe2005.90.2164.072,208,67215-Jun-200603:30Not Applicable
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STATUS

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

To enable this hotfix, you must turn on trace flag 4105 after you apply the hotfix.

For more information, click the following article number to view the article in the Microsoft Knowledge Base:
824684
(http://support.microsoft.com/kb/824684/ )
Description of the standard terminology that is used to describe Microsoft software updates
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Properties

Article ID: 920347 - Last Review: August 31, 2010 - Revision: 2.0
APPLIES TO
  • Microsoft SQL Server 2005 Standard Edition
  • Microsoft SQL Server 2005 Standard X64 Edition
  • Microsoft SQL Server 2005 Standard Edition for Itanium-based Systems
  • Microsoft SQL Server 2005 Enterprise Edition
  • Microsoft SQL Server 2005 Enterprise X64 Edition
  • Microsoft SQL Server 2005 Enterprise Edition for Itanium-based Systems
  • Microsoft SQL Server 2005 Developer Edition
Keywords: 
kbautohotfix kbbug kbfix kbtshoot kbhotfixserver kbqfe KB920347
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