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Re: Free-space-map management thoughts

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Robert Treat <xzilla(at)users(dot)sourceforge(dot)net>
Cc: pgsql-hackers(at)postgresql(dot)org
Subject: Re: Free-space-map management thoughts
Date: 2003-02-27 16:00:11
Message-ID: 11275.1046361611@sss.pgh.pa.us (view raw or flat)
Thread:
Lists: pgsql-hackers
Robert Treat <xzilla(at)users(dot)sourceforge(dot)net> writes:
> Now that indexes are getting some reporting, my understanding is an
> index would report fewer pages overall than it's associated table, but
> those pages would be completely empty.  However, given that they don't
> reported non-empty pages, the percentage of freeable space to total
> space would be unfairly lower (if I'm right in thinking that the back
> end will assume that non-reported pages don't have empty space in them).
> This would tend to hurt index management even though it's pages are the
> best candidates for removal (100% empty). Is this a valid concern, or am
> I misreading something?

I'm not following your point... across relations, the proposed scheme
only considers numbers of pages, not how much space is believed free in
each such page.  If anything I suspect it would over-favor the indexes.

			regards, tom lane

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