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Thread: Bitmap indexes

  1. #1
    Join Date
    Nov 2001
    Hi All:

    I need a small clarification on Bitmap Indexes.


    My table Structure.

    Usage_type not null Primary key
    Used_or_not null check (used_or_not in ('Y','N')

    With this structure I acn insert a null value into Used_or_not

    But my queires or much based on used_or_not, The designer is not
    accepting to change the column used_or_not to Not Null.
    Previously they have created a normal index.
    But now i want to change to Bitmap Index. Will the Null Value in
    the column affect much of the performance of the Bitmap Index.

    Pl. suggest me if Bitamp performance is degraded then what type
    of index will help to increase the perfomance.



    Srinivas Reddy Tatireddy

  2. #2
    Join Date
    Feb 2001
    If the column is not highly update/delete then bitmap is a good choice.
    Even if u have a batch updates and for most of the time it remains read only, even then u should go for bitmap.

    Unique index on 1,2.
    This shall a waste a lot of space, and also if the number of rows are very large and returned rows is also large it is goinf to wasteful.

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