About This Blog

Including my content from SQLBlog.com and some from SQLPerformance.com
Showing posts with label Top. Show all posts
Showing posts with label Top. Show all posts

Thursday 3 May 2012

Parallel Execution Plans Suck

Parallel Execution Plans Suck

Summary: A deep dive into SQL Server parallelism, and a potential performance problem with parallel plans that use TOP.

Wednesday 18 August 2010

Inside the Optimizer: Row Goals In Depth

Inside the Optimizer: Row Goals In Depth

Background

One of the core assumptions made by the SQL Server query optimizer cost model is that clients will eventually consume all the rows produced by a query.

This results in plans that favour the overall execution cost, though it may take longer to begin producing rows.