Date: Mon, 13 Aug 2018 11:46:30 -0300
From: Alvaro Herrera <alvherre@2ndquadrant.com>
To: Tomas Vondra <tomas.vondra@2ndquadrant.com>
Cc: Andres Freund <andres@anarazel.de>,
	PostgreSQL-development <pgsql-hackers@postgresql.org>
Subject: Re: logical decoding / rewrite map vs. maxAllocatedDescs
Message-ID: <20180813144630.hmzdrbviwao64ube@alvherre.pgsql>
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On 2018-Aug-11, Tomas Vondra wrote:

> Hmmm, it's difficult to compare "bt full" output, but my backtraces look
> somewhat different (and all the backtraces I'm seeing are 100% exactly
> the same). Attached for comparison.

Hmm, looks similar enough to me -- at the bottom you have the executor
doing its thing, then an AcceptInvalidationMessages in the middle
section atop which sit a few more catalog accesses, and further up from
that you have another AcceptInvalidationMessages with more catalog
accesses.  AFAICS that's pretty much the same thing Andres was
describing.  I think the exact shape of the executor bits is not
relevant, and I suppose the exact details of what occurs when
invalidation messages are processed are not terribly important either.
I think in Andres' backtrace there are *three*
AcceptInvalidationMessages rather than two as in your case, but that
shouldn't be important either, just the fact that there are N nested
ones.

-- 
Álvaro Herrera                https://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services