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FIX: Different results may be returned when you concurrently run the same query with the RECOMPILE option in SQL Server 2008

Microsoft distributes Microsoft SQL Server 2008 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 2008 fix release.
SYMPTOMS
In Microsoft SQL Server 2008, you have a query that uses the RECOMPILE option. However, if you run the query concurrently in some connections, different results may be returned for the same query.
CAUSE
In SQL Server 2008, an enhancement was introduced which allowed the query optimizer to use the actual parameter values passed when compiling plans for batches executed with the OPTION RECOMPILE syntax. (Parameter Embedding Optimization)

The cause for this problem was the fact that the query optimizer tied plans that had been compiled using this method to a specific thread. However there was no guarantee that the plan compiled on this thread would always execute on the same thread.
RESOLUTION
The fix for this issue was first released in Cumulative Update 5 for SQL Server 2008 Service Pack 1. For more information about this cumulative update package, click the following article number to view the article in the Microsoft Knowledge Base:
975977 Cumulative update package 5 for SQL Server 2008 Service Pack 1
Note Because the builds are cumulative, each new fix release contains all the hotfixes and all the security fixes that were included with the previous SQL Server 2008 fix release. Microsoft recommends that you consider applying the most recent fix release that contains this hotfix. For more information, click the following article number to view the article in the Microsoft Knowledge Base:
970365 The SQL Server 2008 builds that were released after SQL Server 2008 Service Pack 1 was released
Microsoft SQL Server 2008 hotfixes are created for specific SQL Server service packs. You must apply a SQL Server 2008 Service Pack 1 hotfix to an installation of SQL Server 2008 Service Pack 1. By default, any hotfix that is provided in a SQL Server service pack is included in the next SQL Server service pack.
WORKAROUND
To work around this problem, do not use the RECOMPILE option.
STATUS
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.
MORE INFORMATION
This issue was originally resolved in SQL Server 2008 Cumulative Update 4 by removing the parameter embedding optimization routines, or advising not to use the OPTION RECOMPILE syntax.

For more information, visit the following KB article:
968693 FIX: A query that uses parameters and the RECOMPILE option returns incorrect results when you run the query in multiple connections concurrently in SQL Server 2008




Microsoft have now released this fix which is a thorough solution to this problem, which resolves the original incorrect results problem, but also allows the use of the enhanced functionality of the OPTION RECOMPILE syntax introduced in SQL Server 2008.
REFERENCES
For more information about the Incremental Servicing Model for SQL Server, click the following article number to view the article in the Microsoft Knowledge Base:
935897 An Incremental Servicing Model is available from the SQL Server team to deliver hotfixes for reported problems


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:
822499New 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
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Article ID: 976603 - Last Review: 11/16/2009 09:37:02 - Revision: 1.0

Microsoft SQL Server 2008 Standard, Microsoft SQL Server 2008 Enterprise, Microsoft SQL Server 2008 Developer, Microsoft SQL Server 2008 Workgroup

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