FIX: A performance issue occurs when you perform a partition merge operation to move data between partitions in SQL Server 2008

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Article ID: 976379 - View products that this article applies to.
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.
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SYMPTOMS

Consider the following scenario:
  • In Microsoft SQL Server 2008, you have a partitioned table that contains multiple partitions.
  • You try to merge a partition with another partition.

    Note The source partition is in the middle of the table.
  • The size of the source partition is significantly larger than the destination partition. For example, the source partition has many more rows than the destination partition.
In this scenario, the partition merge operation takes longer than expected to be completed.

For example, if the source partition has 10 million rows and the destination partition has 1 million rows, SQL Server moves the 10 million rows that are in the source partition instead of moving the 1 million rows that are in the destination partition. Additionally, SQL Server tracks the moved data in the transaction log. This tracking behavior also affects the performance.

Note This problem also occurs in SQL Server 2005.

RESOLUTION

The fix for this issue was first released in Cumulative Update 6 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:
977443 Cumulative update package 6 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. 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:
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.

This hotfix optimizes the performance of the merge operation by moving data from the smaller partition to the larger partition. However, this optimization is not applicable when you try to merge two partitions that are mapped to different file groups. Therefore, this hotfix works only when the source partition and the destination partition are mapped to the same filegroup. In the special case in which the smaller partition has no rows, the merge operation will change only the metadata.

STATUS

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

REFERENCES

For more information about partition merge operations, visit the following Microsoft Web site:

ALTER PARTITION FUNCTION (Transact-SQL)
For 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:
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

Properties

Article ID: 976379 - Last Review: January 29, 2010 - Revision: 2.0
APPLIES TO
  • Microsoft SQL Server 2008 Standard
  • Microsoft SQL Server 2008 Enterprise
  • Microsoft SQL Server 2008 Developer
  • Microsoft SQL Server 2008 Workgroup
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kbexpertiseadvanced kbsurveynew kbqfe kbfix KB976379

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