| From: | Andres Freund <andres(at)anarazel(dot)de> |
|---|---|
| To: | Kevin Grittner <kgrittn(at)gmail(dot)com> |
| Cc: | Noah Misch <noah(at)leadboat(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>, Ants Aasma <ants(dot)aasma(at)eesti(dot)ee>, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>, Kevin Grittner <kgrittn(at)postgresql(dot)org>, "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Re: [COMMITTERS] pgsql: Avoid extra locks in GetSnapshotData if old_snapshot_threshold < |
| Date: | 2016-07-08 17:53:49 |
| Message-ID: | 20160708175349.ue6okmukiny3r6cp@alap3.anarazel.de |
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| Lists: | pgsql-committers pgsql-hackers |
On 2016-07-08 11:00:50 -0500, Kevin Grittner wrote:
> On Wed, Jul 6, 2016 at 4:55 PM, Andres Freund <andres(at)anarazel(dot)de> wrote:
>
> > So I don't think that approach still allows old snapshot related
> > cleanups for toast triggered vacuums? Is that an acceptable
> > restriction?
>
> What I would rather see is that if the heap is vacuumed (whether or
> not by autovacuum) then the related TOAST table is also vacuumed
> (using the same horizon the heap used), but if the TOAST relation
> is chosen for vacuum by itself that it does not attempt to adjust
> the horizon based on old_snapshot_threshold.
Uh, wouldn't that quote massively regress the autovacuum workload in
some cases? There's a reason they're considered separately after
all. And in many cases, even if there's lots of updates in the heap
table, the toast table doesn't get any updates. And the toast table is
often a lot larger than the data.
Regards,
Andres
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