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  • Fake statistics, and how to get rid of them

    There are two ways to test how your queries behave on huge amounts of data. The simple option is to actually use them on huge amounts of data – but where do you get that if you have no access to the production database, and how do you store it if you happen not to have a multi-terabyte storage array sitting in your basement? So here’s the second ...
  • Skewed Data - Poor Cardinality Estimates... and Plans Gone Bad

    The session Skewed Data, Poor Cardinality Estimates, and Plans Gone Bad by Kimberly Tripp (@KimberlyLTripp) has been published on channel SQLPASS TV.  Abstract When data distribution is heavily skewed, cardinality estimation (how many rows the query optimizer expects each operator to process) can be wildly incorrect, resulting in ...
    Posted to Sergio Govoni (Weblog) by Sergio Govoni on February 14, 2014
  • Parameterization and filtered indexes (part 2)

    In my previous post, I demonstrated how the presence of a filtered index can get in the way of successful parameterization, possibly resulting in too much query compilations and procedure cache bloat. I suggest reading that first, because I will go straight where I left off.   Use the Force, Luke   If you read the previous post very ...
  • Understanding Execution Plans

    To me, it feels as if 2014 is a long time away. But it isn’t. Sinterklaas has already dropped off his presents and is probably already back in his castle in Spain. Christmas is almost upon us. And before we know it, we’ll be washing oliebollen down with Champagne. That also means that I need to get cracking on preparing my precon seminar on ...
  • Comparing multiple plans in SQL Sentry Plan Explorer

    I’ve seen the question a few times now: “How do I compare two plans side-by-side in Plan Explorer?” Management Studio allows you to view multiple graphical plans that are visible simultaneously, either by generating plans for every statement in a batch, or by generating plans in separate query windows and then splitting the panes. However, at ...
    Posted to Aaron Bertrand (Weblog) by AaronBertrand on January 6, 2012
  • Connect Digest : 2011-12-01

    Where is my graphical ShowPlan? Many of you on SQL Server 2008 R2 are experiencing a major annoyance with SSMS since installing service pack 1 - when clicking a plan from grid results, you get raw XML instead of the graphical plan. I wrote about this symptom and a workaround in a previous post. In the original Connect item, they state that it ...
    Posted to Aaron Bertrand (Weblog) by AaronBertrand on December 1, 2011
  • Getting graphical ShowPlans back in SQL Server 2008 R2

    For those of you using the SQL Server 2008 R2 version of Management Studio, and have applied Service Pack 1, you have probably noticed that clicking on a ShowPlan in grid results no longer shows the graphical plan, but rather opens a new window with the raw XML. For example, running the following query: SELECT TOP (5) ...
    Posted to Aaron Bertrand (Weblog) by AaronBertrand on October 28, 2011
  • SQL Sentry Plan Explorer v1.3

    On Friday, we published a new version of our free query plan analysis tool, SQL Sentry Plan Explorer. As noted in the change list, we've added a couple of important features. SQL Server 2012 support With a whole slew of changes to the showplan schema in Denali, we've added operators and columns to reflect these changes. For example, you will ...
    Posted to Aaron Bertrand (Weblog) by AaronBertrand on October 25, 2011
  • Why generalizations are dangerous

    A couple of years ago, John Sansom wrote a blog post comparing the performance of two different ways to get the maximum value from a column: MAX() and TOP (1). http://www.johnsansom.com/performance-comparison-of-select-top-1-verses-max/ In the conclusion, he states:  When a clustered index is present on the table & ...
    Posted to Aaron Bertrand (Weblog) by AaronBertrand on September 15, 2011
  • A demo kit for SQL Sentry Plan Explorer

    UPDATE - This demo kit has been overhauled: http://sqlperformance.com/2014/03/t-sql-queries/updated-plan-explorer-demo-kit   Plan Explorer is a free application from SQL Sentry, designed to make execution plan analysis faster and easier. It was developed in response to customer demand for deeper query analysis, but was ...
    Posted to Aaron Bertrand (Weblog) by AaronBertrand on September 13, 2011
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