| From: | Alvaro Herrera <alvherre(at)2ndquadrant(dot)com> |
|---|---|
| To: | Kevin Grittner <kgrittn(at)ymail(dot)com> |
| Cc: | Bruce Momjian <bruce(at)momjian(dot)us>, Alexey Bashtanov <bashtanov(at)imap(dot)cc>, "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Autovacuum fails to keep visibility map up-to-date in mostly-insert-only-tables |
| Date: | 2014-10-09 21:18:29 |
| Message-ID: | 20141009211829.GK7043@eldon.alvh.no-ip.org |
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| Lists: | pgsql-hackers |
Kevin Grittner wrote:
> Wouldn't we get substantially the same thing just by counting tuple
> inserts toward the autovacuum vacuum threshold? I mean, it unless
> the table is due for wraparound prevention autovacuum, it will only
> visit pages that don't have the all-visible bit set, right? And
> how much work would that do beyond what you're describing if none
> of the tuples are dead?
The problem is precisely what happens if there are some dead tuples, but
not enough to reach the 20% threshold: this vacuum now has to scan the
table twice and has to clean up indexes also.
--
Álvaro Herrera http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services
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