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  • SQL Intersection Conference, Las Vegas MGM Grand 10-13 November 2014

    I am very pleased to announce that I will be speaking at the SQL Intersection conference in Las Vegas again this year. This time around, I am giving a full-day workshop, "Mastering SQL Server Execution Plan Analysis" as well as a two-part session, "Parallel Query Execution" during the main conference. The workshop is a ...
    Posted to Paul White: Page Free Space (Weblog) by Paul White on July 31, 2014
  • Compute Scalars, Expressions and Execution Plan Performance

    The humble Compute Scalar is one of the least well-understood of the execution plan operators, and usually the last place people look for query performance problems.  It often appears in execution plans with a very low (or even zero) cost, which goes some way to explaining why people ignore it. Some readers will already know that a Compute ...
    Posted to Paul White: Page Free Space (Weblog) by Paul White on September 4, 2012
  • Fun with Aggregates

    There are interesting things to be learned from even the simplest queries.  For example, imagine you are given the task of writing a query to list AdventureWorks product names where the product has at least one entry in the transaction history table, but fewer than ten. One possible query to meet that specification is: SELECT ...
    Posted to Paul White: Page Free Space (Weblog) by Paul White on March 11, 2012
  • Forcing a Parallel Query Execution Plan

    This post is for SQL Server developers who have experienced the special kind of frustration, which only comes from spending hours trying to convince the query optimizer to generate a parallel execution plan.  This situation often occurs when making an apparently innocuous change to the text of a moderately complex query; a change which ...
    Posted to Paul White: Page Free Space (Weblog) by Paul White on December 22, 2011
  • How to Find the Statistics Used to Compile an Execution Plan

    In this post, I show you how to determine exactly which statistics objects were used by the query optimizer to produce an execution plan. Trace Flags We will need three undocumented trace flags.  The first one (3604) is well-known – it redirects trace output to the client so it appears in the SSMS messages tab. The second trace flag is ...
    Posted to Paul White: Page Free Space (Weblog) by Paul White on September 20, 2011
  • Heaps of Trouble?

    If you’re not already a regular reader of Brad Schulz’s blog, you’re missing out on some great material.  In his latest entry, he is tasked with optimizing a query run against tables that have no indexes at all.  The problem is, predictably, that performance is not very good.  The catch is that we are not allowed to create any ...
    Posted to Paul White: Page Free Space (Weblog) by Paul White on December 9, 2010
  • A Tale of Two Index Hints

    If you look up Table Hints in Books Online, you’ll find the following statement: If a clustered index exists, INDEX(0) forces a clustered index scan and INDEX(1) forces a clustered index scan or seek. If no clustered index exists, INDEX(0) forces a table scan and INDEX(1) is interpreted as an error. The interesting thing there is ...
    Posted to Paul White: Page Free Space (Weblog) by Paul White on September 22, 2010
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