FIX: Results may change every time that you run a parallel query in SQL Server 2005, in SQL Server 2008, or in SQL Server 2008 R2 if the query uses a ranking function and if the computer has eight or more CPUs

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Article ID: 2546901 - View products that this article applies to.
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Microsoft distributes Microsoft SQL Server 2008 R2 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 R2 fix release.

SYMPTOMS

Consider the following scenario:
  • You run Microsoft SQL Server 2005, Microsoft SQL Server 2008, or Microsoft SQL Server 2008 R2 on a computer that has eight or more CPUs.
  • You run a query that uses a ranking function and a parallel execution plan.

    For example, the query uses the ROW_NUMBER, RANK, NTILE, or DENSE_RANK ranking function, and you set the Max Degree of Parallelism option to 4 in server configuration.
In this scenario, the query may return different results every time that you run the query.

Note This issue may occur in one of the following situations:
  • You set the MAXDOP query hint option to a value that is greater than 2.
  • You set the Max Degree of Parallelism option to a value that is greater than 2.

RESOLUTION

Service pack information

To resolve this issue, obtain the latest service pack for SQL Server 2008 R2, and then enable the 4134 trace flag.

For more information, click the following article number to view the article in the Microsoft Knowledge Base: 
2527041 How to obtain the latest service pack for SQL Server 2008 R2
For more information about how to switch on the 4134 trace flag, visit the following MSDN website:

How to switch on the 4134 trace flag

STATUS

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

MORE INFORMATION

For more information about ranking functions, visit the following MSDN website: 

General information about ranking functions
For more information about parallel query processing, visit the following MSDN website:
General information about parallel query processing
For more information about the max degree of parallelism option, visit the following TechNet website:
General information about the max degree of parallelism option

Properties

Article ID: 2546901 - Last Review: July 20, 2011 - Revision: 2.0
APPLIES TO
  • Microsoft SQL Server 2008 R2 Datacenter
  • Microsoft SQL Server 2008 R2 Developer
  • Microsoft SQL Server 2008 R2 Enterprise
  • Microsoft SQL Server 2008 R2 Express
  • Microsoft SQL Server 2008 R2 Express with Advanced Services
  • Microsoft SQL Server 2008 R2 Standard
  • Microsoft SQL Server 2008 R2 Standard Edition for Small Business
  • Microsoft SQL Server 2008 R2 Web
  • Microsoft SQL Server 2008 R2 Workgroup
Keywords: 
kbqfe kbexpertiseadvanced kbsurveynew kbfix KB2546901

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