Re: Bitmap Indexes: request for feedback

Josh Berkus <josh(at)agliodbs(dot)com> writes:

> Gianni,
>
>> me and Gabriele Bartolini have been working on Bitmap Indexes (BMI) in
>> the last weeks, with advice and guidance from Simon Riggs. We feel
>> that we are about to approach the point where it is appropriate to ask
>> for feedback from this list.
>
> The other major issue with the Bitmap index patch as it stood in 2007 was
> that performance just wasn't that much faster than a btree, except for
> specific corner cases. Otherwise, someone else would have been interested
> enough to pick it up and finish it.

Actually as I recall the immediate issue was that the patch was more complex
than necessary. In particular it reimplemented parts of the executor
internally rather than figuring out what api was necessary to integrate it
fully into the executor.

When we last left our heros they were proposing ways to refactor the index api
to allow index ams to stream results to the executor in bitmap form. That
would allow a scan of a bitmap index to return bitmap elements wholesale and
have the executor apply bitmap operations to them along with the elements
returned by a btree bitmap scan or other index ams.

--
Gregory Stark
EnterpriseDB http://www.enterprisedb.com
Ask me about EnterpriseDB's On-Demand Production Tuning