Re: Free-space-map management thoughts - Mailing list pgsql-hackers

From Tom Lane
Subject Re: Free-space-map management thoughts
Date
Msg-id 11275.1046361611@sss.pgh.pa.us
Whole thread Raw
In response to Re: Free-space-map management thoughts  (Robert Treat <xzilla@users.sourceforge.net>)
Responses Re: Free-space-map management thoughts
List pgsql-hackers
Robert Treat <xzilla@users.sourceforge.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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