| From: | Andres Freund <andres(at)2ndquadrant(dot)com> |
|---|---|
| To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | Mark Kirkwood <mark(dot)kirkwood(at)catalyst(dot)net(dot)nz>, pgsql-hackers(at)postgresql(dot)org, "Joshua D(dot) Drake" <jd(at)commandprompt(dot)com> |
| Subject: | Re: Why do we let autovacuum give up? |
| Date: | 2014-01-23 23:55:21 |
| Message-ID: | 20140123235521.GM7182@awork2.anarazel.de |
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| Lists: | pgsql-hackers |
On 2014-01-23 16:15:50 -0500, Tom Lane wrote:
> [ thinks... ] It's possible that what you saw is not the
> kick-out-autovacuum-entirely behavior, but the behavior added in commit
> bbb6e559c, whereby vacuum (auto or regular) will skip over pages that it
> can't immediately get an exclusive buffer lock on. On a heavily used
> table, we might skip the same page repeatedly, so that dead tuples don't
> get cleaned for a long time.
I don't think it's too likely as an explanation here. Such workloads are
likely to fill a page with only dead tuples, right? Once all tuples are
safely dead they will be killed from the btree which should cause the
page not to be visited anymore and thus safely vacuumable.
Greetings,
Andres Freund
--
Andres Freund http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services
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