Re: When do vacuumed pages/tuples become available for reuse?

From: Michael Paquier <michael(at)paquier(dot)xyz>
To: Michael Lewis <mlewis(at)entrata(dot)com>
Cc: Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>, rihad <rihad(at)mail(dot)ru>, Jeff Janes <jeff(dot)janes(at)gmail(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, pgsql-general General <pgsql-general(at)postgresql(dot)org>
Subject: Re: When do vacuumed pages/tuples become available for reuse?
Date: 2019-04-12 04:07:27
Message-ID: 20190412040727.GH2144@paquier.xyz
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On Thu, Apr 11, 2019 at 11:13:17AM -0600, Michael Lewis wrote:
> Wouldn't "dead but not yet removable" be high if there were long running
> transactions holding onto old row versions?

You got it right. You need to look at the number behind the tuples
dead, but not removable which is usually a pattern caused by long
running transactions holding snapshot references which prevents
autovacuum and/or vacuum to do their homework.
--
Michael

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