Re: Bitmap indexes

From: Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us>
To: PFC <lists(at)boutiquenumerique(dot)com>
Cc: PostgreSQL Perfomance <pgsql-performance(at)postgresql(dot)org>
Subject: Re: Bitmap indexes
Date: 2005-02-02 16:08:09
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PFC wrote:
> > There's a great deal about this in the list archives (probably more in
> > pgsql-hackers than in -performance). Most of the current interest has
> > to do with building in-memory bitmaps on the fly, as a way of decoupling
> > index and heap scan processing. Which is not quite what you're talking
> > about but should be pretty effective for low-cardinality cases. In
> > particular it'd allow AND and OR combination of multiple indexes, which
> > we do poorly or not at all at the moment.
> Is this called a star join ?
> It would also allow to access the data pages in a more sequential order
> if the rows are not required to be retrieved in index order, which would
> potentially be a large speedup for index scans concerning more than the
> usual very small percentage of rows in a table : if several rows to be
> retrieved are on the same page, it would visit this page only once.

Please see the TODO list for a summary of previous discussions and

Bruce Momjian |
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