Re: Implementing Bitmap Indexes

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Mike Rylander <mrylander(at)gmail(dot)com>
Cc: Pawe� Niewiadomski <new(at)foo-baz(dot)com>, Postgres Hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Implementing Bitmap Indexes
Date: 2005-01-29 21:21:09
Message-ID: 10262.1107033669@sss.pgh.pa.us
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Mike Rylander <mrylander(at)gmail(dot)com> writes:
> As a side note, wouldn't the in-memory bitmaps pretty much kill the
> need for multicolumn indexes? It seems that they would be able to
> join index scans on the same table, and then there would be no need
> for industrial strength cross-column correlation stats.

No, because the ability to do it is not the same as the ability to
predict in advance how many rows will result.

regards, tom lane

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