February 2013 - SQLPerformance.com

A Look At DBCC CHECKCONSTRAINTS and I/O

Erin Stellato of SQLskills takes a deep look into the I/O impact of running DBCC CHECKCONSTRAINTS, including explaining why some check methods may consume a lot more I/O than others.

Erin Stellato ◆ February 28, 2013

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2013 MVP Summit : A quick review and a peek forward

I had a great time at the MVP Summit last week. Caught up with a lot of friends, tried some new foods (including Tempura Fried Kurobuta Bacon), and took in some great technical sessions.

Aaron Bertrand ◆ February 25, 2013

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Transaction Log Configuration Issues

Paul Randal of SQLskills continues his series on maintaining happy and healthy transaction logs in SQL Server, this time focusing on configuration issues that can lead to less than optimal performance.

Paul Randal ◆ February 22, 2013

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The Halloween Problem – Part 4

The Halloween Problem has a number of important consequences for SQL Server execution plans. In this final part of the series, we look at some of the tricks the optimizer uses to avoid adding an Eager Table Spool to every update query that might encounter the Halloween Problem.

Paul White ◆ February 20, 2013

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The Halloween Problem – Part 3

The MERGE statement (introduced in SQL Server 2008) allows us to perform a mixture of INSERT, UPDATE, and DELETE operations using a single declarative statement. The Halloween Protection issues for MERGE are, logically enough, mostly a combination of the requirements for the individual operations performed, but there are some important differences and a couple of optimizations that apply only to MERGE.

Paul White ◆ February 18, 2013

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The Halloween Problem – Part 2

In the first part of this series, we saw how the Halloween Problem applies to UPDATE queries. In this post, we will see how the same underlying issue can affect INSERT and DELETE statements.

Paul White ◆ February 15, 2013

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The Halloween Problem – Part 1

Much has been written over the years about understanding and optimizing SELECT queries, but rather less about data modification. This series of posts looks at an issue that is specific to INSERT, UPDATE, DELETE and MERGE queries – the Halloween Problem.

Paul White ◆ February 13, 2013

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If you are using indexed views and MERGE, please read this!

Here is some information about an important MERGE "wrong results" bug, involving indexed views, that could be affecting the accuracy of your queries right now, and what options you have for working around the problem.

Aaron Bertrand ◆ February 6, 2013

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