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  • Deletes that Split Pages and Forwarded Ghosts

    Can DELETE operations cause pages to split?  Yes.  It sounds counter-intuitive on the face of it; deleting rows frees up space on a page, and page splitting occurs when a page needs additional space.  Nevertheless, there are circumstances when deleting rows causes them to expand before they can be deleted.  The mechanism at ...
    Posted to Paul White: Page Free Space (Weblog) by Paul White on August 30, 2012
  • Can a SELECT query cause page splits?

    Books Online has this to say about page splits: When a new row is added to a full index page, the Database Engine moves approximately half the rows to a new page to make room for the new row.  This reorganization is known as a page split.  A page split makes room for new records, but can take time to perform and is a resource ...
    Posted to Paul White: Page Free Space (Weblog) by Paul White on August 29, 2011
  • SQL Server, Seeks, and Binary Search

    The following table summarizes the results from my last two blog entries, showing the CPU time used when performing 5 million clustered index seeks: In test 1, making the clustered index unique improved performance by around 40%. In test 2, making the same change reduced performance by around 70% (on 64-bit systems – more on that later).  ...
    Posted to Paul White: Page Free Space (Weblog) by Paul White on August 8, 2011
  • Join Performance, Implicit Conversions, and Residuals

    You probably already know that it’s important to be aware of data types when writing queries, and that implicit conversions between types can lead to poor query performance.  Some people have gone so far as to write scripts to search the plan cache for CONVERT_IMPLICIT elements, and others routinely inspect plans for that type of thing when ...
    Posted to Paul White: Page Free Space (Weblog) by Paul White on July 18, 2011
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