Microsoft distributes Microsoft SQL Server 2008 R2 Service Pack 1 (SP1) or Microsoft SQL Server 2012 fixes in one downloadable file. Because the fixes are cumulative, each new release contains all the hotfixes and all the security updates that were included with the previous SQL Server 2008 R2 Service Pack 1 (SP1) or Microsoft SQL Server 2012 update release.
Symptoms
When you run a parallel query that contains a common language runtime (CLR) user-defined aggregate (UDA) function in Microsoft SQL Server 2008 R2, a System.NullReferenceException exception or a System.InvalidOperationException exception might occur. Additionally, you receive the following error message:
Msg 6522, Level 16, State 2, Line 1
A .NET Framework error occurred during execution of user-defined routine or aggregate "<user-defined routine or aggregate name>": System.NullReferenceException: Object reference not set to an instance of an object.Resolution
Cumulative update information
SQL Server 2012
The fix for this issue was first released in Cumulative Update 1 for SQL Server 2012. For more information about this cumulative update package, click the following article number to view the article in the Microsoft Knowledge Base:
2679368 Cumulative update package 1 for SQL Server 2012Note 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 2012 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:
2692828 The SQL Server 2012 builds that were released after SQL Server 2012 was released You must apply a SQL Server 2012 hotfix to an installation of SQL Server 2012.
Cumulative update package 5 for SQL Server 2008 R2 SP1
The fix for this issue was first released in Cumulative Update 5. For more information about how to obtain this cumulative update package for SQL Server 2008 R2 SP1, click the following article number to view the article in the Microsoft Knowledge Base:
2659694 Cumulative update package 5 for SQL Server 2008 R2 SP1Note 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 R2 SP1 fix release. We recommend 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:
2567616 The SQL Server 2008 R2 builds that were released after SQL Server 2008 R2 SP1 was released
Workaround
To work around this issue, do not run a query that uses a parallel execution plan.
For example, you can set the max degree of parallelism option to 1 in the server configuration or set the MAXDOP query hint option to 1.More Information
For more information about CLR UDA, visit the following MSDN website:
Status
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.