Re: Best way to scan on-disk bitmaps

From: "Victor Y(dot) Yegorov" <viy(at)mits(dot)lv>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Postgres Hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Best way to scan on-disk bitmaps
Date: 2005-05-12 21:27:01
Message-ID: 20050512212701.GB18096@mits.lv
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* Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> [12.05.2005 23:09]:
> 1. Be sure that all the indexable WHERE conditions are passed to the
> indexscan as indexquals. This might be, say,
> WHERE a = 42 and b = 'foo'

If I have on-disk bitmap
ON (a, b, c)
will the planner pick an index scan for
WHERE a = 42 AND b = 'foo'
(i.e. only part of the index attributes are involved)? Any modifications
needed to achieve this functionality?

To my mind, bitmap scan even for 1 attribute of a multi-column index would be
a win, though I haven't tested this yet.

--

Victor Y. Yegorov

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