NORECOMPUTE option of UPDATE STATISTICS in SQL Server


By:   |   Updated: 2006-10-04   |   Comments (2)   |   Related: More > Performance Tuning


Problem

Updating statistics is valuable for ensuring the SQL Server optimizer has the current statistical information to most efficiently process the query results.  As a best practice, the UPDATE STATISTICS command should be issued on a regular basis to provide SQL Server with the most recent data.  Automatically updating statistics is possible with the 'Auto Update Statistics' database configuration, but this could cause performance issues if a large table's statistics are updated during the middle of the day.  To prevent this problem, the 'Auto Update Statistics' option can be disabled on a per database basis. This paradigm creates the need to rebuild all of the statistics in a manual manner.  Does a happy medium exist to let SQL Server automatically manage the statistics on small tables and let me manage the statistics on the larger tables?

Solution

The simple answer is 'yes'.  SQL Server statistics can be configured on a per database basis with the ability to not automatically re-compute indexes on larger tables with the NORECOMPUTE option of the UPDATE STATISTICS command.  So let's break down the configurations and commands to make this a reality. 

Where can I find the auto update statistics option? 

SQL Server 2000 - Database Properties
SQL Server 2005 - Database Properties

How can I incorporate the NORECOMPUTE option of the UPDATE STATISTICS command in my code?

SQL Server 2000 SQL Server 2005
UPDATE STATISTICS dbo.Authors WITH NORECOMPUTE
GO
UPDATE STATISTICS dbo.Customer WITH NORECOMPUTE;
GO

Are any commands available to update the statistics in a simple manner?

SQL Server 2000 SQL Server 2005
master.dbo.sp_updatestats master.sys.sp_updatestats

How can I re-enable Auto Update Statistics once I have used the NORECOMPUTE option?

SQL Server 2000 SQL Server 2005
master.dbo.sp_autostats master.sys.sp_autostats
Next Steps
  • Review the 'Auto Update Statistics' option for your database to determine if the configurations are as expected.
  • Determine how statistics are currently being updated and how to best handle this portion of the SQL Server maintenance process.
  • If you are not currently performing SQL Server maintenance including updating the statistics, then take the time to build a maintenance process for your databases.
  • If you have Auto Update Statistics enabled on all of your large databases and are not experiencing any issues consider re-evaluating this approach and use the NORECOMPUTE option of the UPDATE STATISTICS command for the large tables and let SQL Server maintain the statistics for the small tables.
  • Thank you to Armando from the MSSQLTips.com community for sharing this tip idea.  If you would like to share tips of your own, please email your ideas to [email protected].


Last Updated: 2006-10-04


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About the author
MSSQLTips author Jeremy Kadlec Jeremy Kadlec is the Co-Founder, Editor and Author at MSSQLTips.com, CTO @ Edgewood Solutions and a six time SQL Server MVP.

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Comments For This Article




Tuesday, April 24, 2012 - 8:59:13 PM - Jeremy Kadlec Back To Top (17090)

To whom it may concern:

Here are a few items to check out:

Start with these few items and let me know what you find out.

Thank you,
Jeremy Kadlec


Tuesday, April 24, 2012 - 3:46:05 PM - it_is_me Back To Top (17084)

My dear fellow DBA's.  I have a ?.  I have the following query in SQL SERVER 2008 R2:

select top 50 * from myview      and it runs in less than 3 sec.

I then change my query to select top 50 * from myview ORDER BY col4 and it runs forever.  My user claim it has been working ok in the past, but last night we failed over to another instance in the cluster.  I am trying to figure out why the query is taking too long when selecting and ORDERing from the view.  I'am at a brick wall.

Any comments anybody



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