Microsoft KB Archive/940128

= FIX: When you run a complex query in SQL Server 2005, the query performance is slow if the execution plan of the query contains semi join operators =

Article ID: 940128

Article Last Modified on 11/21/2007

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APPLIES TO


 * Microsoft SQL Server 2005 Developer Edition
 * Microsoft SQL Server 2005 Enterprise Edition
 * 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 X64 Edition
 * Microsoft SQL Server 2005 Enterprise Edition for Itanium-based Systems

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Bug #: 50001440 (SQL Hotfix)



Notice
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.



SUMMARY
This article describes the following about this hotfix release:
 * The issues that are fixed by the hotfix package
 * The prerequisites for installing the hotfix package
 * Whether you must restart the 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



SYMPTOMS
You have a complex query in Microsoft SQL Server 2005. The execution plan of the query contains semi join operators. When you run the query, the query performance of the query is slow compared to Microsoft SQL Server 2000.

Note Typically, semi join operators are generated when the query contains the IN keyword or the EXISTS keyword.



CAUSE
This problem occurs because the query optimizer generates many more execution plans than SQL Server 2000 does. Therefore, the query optimizer may time out. When this occurs, the query optimizer stops searching for executing plans before the query optimizer fully searches all possible executing plans.

To determine whether the query optimizer times out, search for the StatementOptmEarlyAbortReason=&quot;TimeOut&quot; expression in the XML output of the Showplan execution plan.



Hotfix information
A supported hotfix is now 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 service pack that contains this hotfix.

To resolve this problem, submit a request to Microsoft Online Customer Services to obtain the hotfix. To submit an online request to obtain the hotfix, visit the following Microsoft Web site:

http://go.microsoft.com/?linkid=6294451

Note If additional issues occur or 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. To create a separate service request, visit the following Microsoft Web site:

http://support.microsoft.com/contactus/?ws=support

Prerequisites
 SQL Server 2005 Service Pack 2

For more information about how to obtain SQL Server 2005 Service Pack 2, click the following article number to view the article in the Microsoft Knowledge Base:

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.

Hotfix replacement information
This hotfix is not replaced by any other hotfix.

Registry information
You do not have to change the registry.

File information
This hotfix contains only those files that are required to correct the issues that this article lists. This hotfix may not contain 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, Itanium architecture version


WORKAROUND
To work around this problem, avoid using the IN keyword or the EXISTS keyword.



STATUS
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the &quot;Applies to&quot; section.



MORE INFORMATION
After you apply this hotfix, you must enable trace flag 4102 and trace flag 4118 so that the behavior reverts to the behavior in SQL Server 2000. However, we recommend that you use the method that is described in the &quot;Workaround&quot; section before you apply this hotfix.

You must use these trace flags for a connection on the server or for all connections on the server. If you set the trace flags at startup, the trace flags affect all connections on the server.

For more information about how to set trace flags, see the following topics in SQL Server 2005 Books Online:
 * DBCC TRACEON (Transact-SQL)
 * Trace flags (Transact-SQL)
 * DBCC TRACESTATUS (Transact-SQL)
 * Breaking changes to Database Engine features in SQL Server 2005

For more information about the naming schema for SQL Server updates, click the following article number to view the article in the Microsoft Knowledge Base:

822499 New naming schema for Microsoft SQL Server software update packages

For more information about software update terminology, 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

Keywords: kbfix kbqfe kbpubtypekc kbexpertiseadvanced kbhotfixserver kbsql2005engine KB940128

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