About This Blog

SQL Server internals information including my content from SQLBlog.com and SQLPerformance.com.
Showing posts with label Internals. Show all posts
Showing posts with label Internals. Show all posts

Thursday, 29 July 2010

Inside the Optimizer: Constructing a Plan - Part 1

Inside the Optimizer: Constructing a Plan - Part 1

For today’s entry, I thought we might take a look at how the optimizer builds an executable plan using rules. To illustrate the process performed by the optimizer, we will configure it to produce incrementally better plans by progressively applying the necessary rules.

Wednesday, 28 July 2010

Partitioning and the Common Subexpression Spool

Partitioning and the Common Subexpression Spool

SQL Server 2005 introduced the OVER clause to enable partitioning of rowsets before applying a window function. This post looks at how this feature may require a query plan containing a ‘common subexpression spool’. This query plan construction is required whenever an aggregate window function or the NTILE ranking window function is used.