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  • Parallel Execution Plans Suck

    Summary: A deep dive into SQL Server parallelism, and a potential performance problem with parallel plans that use TOP. There was an interesting question asked by Mark Storey-Smith on dba.stackexchange.com back in October 2011.  He was looking at the execution plan for a query that counts a million rows from a virtual auxiliary table of ...
    Posted to Paul White: Page Free Space (Weblog) by Paul White on May 2, 2012
  • Inside the Optimizer: Row Goals In Depth

    Background One of the core assumptions made by the SQL Server query optimiser’s model is that clients will consume all of 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.  Let’s look at an example: The optimiser chooses to perform the ...
    Posted to Paul White: Page Free Space (Weblog) by Paul White on August 18, 2010
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