Difference between Full scan and Fast full scan?
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Thread: Difference between Full scan and Fast full scan?

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  1. #1
    Join Date
    Dec 2005
    Posts
    195

    Difference between Full scan and Fast full scan?

    Dear all, I read the below link.

    http://www.lc.leidenuniv.nl/awcourse...3/optimops.htm

    Here is what understood.

    Fast full index scan

    Fast full scan is used when all the columns in query is existing in index segment. It reads the entire index by using multiblock reads and can be parallelizd.

    My question is what is the difference between full scan and fast full index scan? My understanding is, full index scan is same as fast full index scan. Only diffence is, index full scan does not use muliblock read count. Is this correct? Am i missing any other point here??

  2. #2
    Join Date
    Sep 2002
    Location
    England
    Posts
    7,331
    one full scans the table, the other full scans the index which is 'faster' hence the name

  3. #3
    Join Date
    Dec 2005
    Posts
    195
    Thanks. It makes sense.

  4. #4
    Join Date
    Jun 2000
    Location
    Madrid, Spain
    Posts
    7,448
    well you index full scan as well, used for exmaple in MAX(), MIN() and it does single block scans in b-tree ordered fashion whereas fast full scan I think it just do multiblock reads without any order

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