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 |
Message-ID: | 200502021608.j12G89M04048@candle.pha.pa.us |
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Lists: | pgsql-performance |
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
directions.
--
Bruce Momjian | http://candle.pha.pa.us
pgman(at)candle(dot)pha(dot)pa(dot)us | (610) 359-1001
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