Re: Bitmap index status

Luke Lonergan wrote:
> Mark,
>
> On 9/25/06 11:32 AM, "Mark Wong" <markw(at)osdl(dot)org> 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.

Oh right, people keep telling me that and it keeps going in one ear and
out the other...

> 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.

Great, I'll keep my eye for those. :)

> 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.

Mark