Re: Bitmap Indexes with Star Transformation Enabled

I think you will find that if you have only a two table join, then a star transformation is never considered.

Bear in mind, also, that bitmap indexes are only useful when used in combination - a single bitmap index is likely to be too inefficient to be of any use, so a single dimension join to the fact table is likely to execute as a hash join.

In the event that several dimensions are used to join to a fact table, Oracle is able to use a b-tree to bitmap transformation to combine a b-tree index with other bitmap indexes.

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Donna wrote in message <79808a91.0202251328.1514910a_at_posting.google.com>...


>Do bitmap indexes perform/join differently when all joins are

>bitmap indexes (as opposed to some being b-tree and some being bitmap).

>

>I understand that bitmaps must be chosen based on low cardinality but if

there


>is one dimension table and one fact table being joined and ALL of the

indexes


>used on the fact table are bitmap, does the star transformation parameter

>handle the execution plan differently than it would if some fact indexes

were


>b-tree?

>

>Thanks

>Donna