From: Tom Lane <tgl@sss.pgh.pa.us>
To: Alvaro Herrera <alvherre@2ndquadrant.com>
cc: Kouber Saparev <kouber@gmail.com>, pgsql-admin@postgresql.org
Subject: Re: VACUUM unable to accomplish because of a non-existent MultiXactId
In-reply-to: <20151127195328.GE4320@alvherre.pgsql>
References: <62FE8F79-7278-4AE0-9FDE-0C0277A7B609@gmail.com>
 <20151127184936.GD4320@alvherre.pgsql> <5403.1448652828@sss.pgh.pa.us>
 <20151127195328.GE4320@alvherre.pgsql>
Comments: In-reply-to Alvaro Herrera <alvherre@2ndquadrant.com>
 message dated "Fri, 27 Nov 2015 16:53:28 -0300"
Date: Fri, 27 Nov 2015 15:35:26 -0500
Message-ID: <8089.1448656526@sss.pgh.pa.us>
Precedence: bulk
Sender: pgsql-admin-owner@postgresql.org

Alvaro Herrera <alvherre@2ndquadrant.com> writes:
> Tom Lane wrote:
>> Couldn't creation and deletion of a toasted object within the same
>> transaction do it?

> I tried and couldn't find a way to cause one to appear.  When a row is
> created, it has xmax=0 so when it's deleted the xmax can just be set to
> the deleting xact.  And we don't ever update pg_toast rows, AFAIK.

Ah, nevermind, brain fade ... I was momentarily confusing this with
combo CIDs.  Right, there are no updates or row locks taken on toast
table rows (unless someone were to do one manually?)

			regards, tom lane


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