SQL Not Using the Index, sometimes

  • yup - that's one area that doesn't seem to have changed much.

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    Your lack of planning does not constitute an emergency on my part...unless you're my manager...or a director and above...or a really loud-spoken end-user..All right - what was my emergency again?

  • This leads into the Fill Factor option. I think the default is 0 (effectively 100 %). In an application with lots of I/O, would 80% be better ?

  • homebrew01 (12/30/2008)


    This leads into the Fill Factor option. I think the default is 0 (effectively 100 %). In an application with lots of I/O, would 80% be better ?

    That's usually a reasonable place to start, but it could depend on a lot of factors.

    If the data doesn't get updated a lot (or doesn't have variable-length fields), and the inserting happens mostly "at the end", you may not see a lot of fragmentation. On the other hand, lots of variable-length fields that get updated/lots of inserts into the "middle" of the clustered indexing scheme, or - fewer changes but rather large row sizes could push the fragmentation up.

    Of course - dropping your fill factor too low means less data per page, and therefore indexing and data access becomes less efficient.

    This is where it can get to be a little more art than science. Find the middle area with the least amount of pain:)....

    ----------------------------------------------------------------------------------
    Your lack of planning does not constitute an emergency on my part...unless you're my manager...or a director and above...or a really loud-spoken end-user..All right - what was my emergency again?

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