Re: Bitmap indexes - when to use?

In this case, I say go with nromal B-Tree index. Bitmap is suitable for:

- low-cardinality columns  e.g Yes/No, Married/Single, Male/Female.
- Efficient for queries using OR predicates
- Usefull for DSS (Decesion support system)
-Infrequent updates

NOTE that updates to key columns in a bitmap index is very expensive because bitmaps use bit-segment-level locking. Because locks are acquired on the whole bitmap segment, a row that is covered by the bitmap cannot be updated by other transactions until the first transaction ends.

MKB wrote in message <37443072.EA1CF508_at_mci.com>...
>I'd like to know if using bitmap indexes on a column such as STATE would
>be a good idea. My impression is that bitmaps would be useful only in
>situations with low cardinality in the column (yes/no, on/off etc).
>With a STATE column in a table of, say, 6 million rows, you could have,
>at most, 50 distinct values. Would it be better in this case just to go
>with a regular B-tree index? BTW, in this case the STATE column in the
>main table is an FK to the STATE_CD lookup table and this is for a DSS
>type db using partitions.
>
>(Oracle 8.0.5 on Solaris)
>
>Any input appreciated.
>
>Thanks
>
>mkb
>
>
Received on Thu May 20 1999 - 18:33:50 CDT