Mark, On 9/25/06 11:32 AM, "Mark Wong" <[EMAIL PROTECTED]> wrote:
> Yeah, basically gather as many stats as I can to accurately profile the > overall system performance. I thought it would be appropriate to use a > TPC-H based workload as one measuring stick to use for bitmap indexes. Note that the TPC-H queries don't follow the typical good use case for bitmap indexes. You'd like to see queries that use multiple AND and OR clauses, otherwise there may be no benefit. Also, DBT-3/TPC-H on Postgres right now does not benefit from indices overall. The planner has limitations WRT selectivity estimates and other limitations that cause it to choose index access poorly for the query workload. We have two new features coming (for 8.3) that fix this, but for now we find that indexes are a net loss, in some queries a huge loss. If you look at the whitepaper that Ayush Parashar published, he uses the TPC-H data with some targeted queries that showcase the best use-cases for bitmap index. - Luke ---------------------------(end of broadcast)--------------------------- TIP 6: explain analyze is your friend
