Re: Bitmap Index
- From: Connor McDonald <mcdonald.connor@xxxxxxxxx>
- To: oracle-l@xxxxxxxxxxxxx
- Date: Wed, 12 Oct 2005 08:52:32 +0800
w.r.t "In your case, i'd definitely say your data has low enough cardinality to warrant a bitmap index." I don't have the details to hand, but I've seen and replicated benchmarks that show for querying data, then even up to cardinality of n/2 (n=table rows), then bitmap index outperformed a b-tree index. Its typically not cardinality that matters - the real benefit of bitmaps comes when you can combine them, or you can scan them *instead* of the table to get data (because they're typically so much smaller). Its this versus the concurrency limitations that you need decide on hth -- Connor McDonald =========================== email: connor_mcdonald@xxxxxxxxx web: http://www.oracledba.co.uk "Semper in excremento, sole profundum qui variat"