From: | Andres Freund <andres(at)2ndquadrant(dot)com> |
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To: | Alvaro Herrera <alvherre(at)2ndquadrant(dot)com> |
Cc: | Bruce Momjian <bruce(at)momjian(dot)us>, Robert Haas <robertmhaas(at)gmail(dot)com>, Peter Geoghegan <peter(at)2ndquadrant(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Andrew Dunstan <andrew(at)dunslane(dot)net>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: [PERFORM] encouraging index-only scans |
Date: | 2013-09-06 13:08:54 |
Message-ID: | 20130906130854.GB600952@alap2.anarazel.de |
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Lists: | pgsql-hackers pgsql-performance |
On 2013-09-06 01:22:36 -0400, Alvaro Herrera wrote:
> I think it's shortsighted to keep thinking of autovacuum as just a way
> to run VACUUM and ANALYZE. We have already discussed work items that
> need to be done separately, such as truncating the last few empty pages
> on a relation that was vacuumed recently. We also need to process a GIN
> index' pending insertion list; and with minmax indexes I will want to
> run summarization of heap page ranges.
Agreed.
> So maybe instead of trying to think of VM bit setting as part of vacuum,
> we could just keep stats about how many pages we might need to scan
> because of possibly needing to set the bit, and then doing that in
> autovacuum, independently from actually vacuuming the relation.
I am not sure I understand this though. What would be the point to go
and set all visible and not do the rest of the vacuuming work?
I think triggering vacuuming by scanning the visibility map for the
number of unset bits and use that as another trigger is a good idea. The
vm should ensure we're not doing superflous work.
Greetings,
Andres Freund
--
Andres Freund http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services
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