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Re: Bitmap indexes

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: alex(at)neteconomist(dot)com
Cc: PostgreSQL Perfomance <pgsql-performance(at)postgresql(dot)org>
Subject: Re: Bitmap indexes
Date: 2005-01-28 16:13:46
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-performance
Alex Turner <armtuk(at)gmail(dot)com> writes:
> I was wondering about index types.  Oracle has an index type called a
> 'bitmap' index.

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.

			regards, tom lane

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