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Showing page 2 of 4 (33 total posts)
  • 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
  • Oracle Index Skip Scan

    There is a feature, called index skip scan that has been in Oracle since version 9i. When I across this, it seemed like a very clever trick, but not a critical capability. More recently, I have been advocating DW on SSD in approrpiate situations, and I am thinking this is now a valuable feature in keeping the number of nonclustered indexes ...
    Posted to Joe Chang (Weblog) by jchang on June 12, 2011
  • New Book on the Query Optimizer

      A friend of mine Benjamin Nevarez has written a book on the inner workings of the Query Optimizer and it was just released. I read a preview and was definitely impressed so I expect the full version to be just as good. More details can be found here and it is available at Amazon here as well. I hope you enjoy it. Andy
    Posted to Andrew Kelly (Weblog) by Andrew Kelly on April 9, 2011
  • Advanced TSQL Tuning: Why Internals Knowledge Matters

    There is much more to query tuning than reducing logical reads and adding covering nonclustered indexes.  Query tuning is not complete as soon as the query returns results quickly in the development or test environments.  In production, your query will compete for memory, CPU, locks, I/O and other resources on the server.  Today’s ...
    Posted to Paul White: Page Free Space (Weblog) by Paul White on February 22, 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
  • Inside the Optimizer: Plan Costing

    Summary: A detailed look at costing, and more undocumented optimizer fun. The SQL Server query optimizer generates a number of physical plan alternatives from a logical requirement expressed in T-SQL.  If full cost-based optimization is required, a cost is assigned to each iterator in each alternative plan, and the plan with the lowest ...
    Posted to Paul White: Page Free Space (Weblog) by Paul White on September 1, 2010
  • Inside the Optimizer: Constructing a Plan – Part 4

    Summary: More undocumented ways to explore how the query optimiser works. This post is part of a series: Part1 Part 2 Part3 Part4 Documented Rule-Affecting Options It might surprise you to learn that most T-SQL users have written queries that disable one or more of the optimiser rules already. Join hints { LOOP | HASH | MERGE | ...
    Posted to Paul White: Page Free Space (Weblog) by Paul White on July 31, 2010
  • Speaking at SQLSaturday #44 in Huntington Beach, CA (Los Angeles Area)

      I'll be presenting a session at SQLSaturday #44 in Huntington Beach, the first SQLSaturday on Southern California. The event takes place on Saturday, April 24 at the Golden West College on 15744 Goldenwest St, Huntington Beach, CA 92647.. For more information visit the following ...
    Posted to Benjamin Nevarez (Weblog) by Ben Nevarez on April 15, 2010
  • The Query Optimizer and Cost Estimation

    Last year when I presented my session regarding the Query Optimizer at the PASS Summit and at a couple of local user groups, I was asked how the estimated CPU and I/O costs in an execution plan are calculated. Since Microsoft does not publish how these costs are calculated all I could say was that each operator cost depends on the operator ...
    Posted to Benjamin Nevarez (Weblog) by Ben Nevarez on February 17, 2010
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