Halloween problem Archives - SQLPerformance.com

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

15

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

4

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

4

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

9