From: Stephen Frost <sfrost@snowman.net>
To: Andreas Joseph Krogh <andreas@visena.com>
Cc: Bruce Momjian <bruce@momjian.us>
Cc: Michael Paquier <michael.paquier@gmail.com>
Cc: Robert Haas <robertmhaas@gmail.com>
Cc: pgsql-hackers@postgresql.org <pgsql-hackers@postgresql.org>
Subject: Re: Clarification in pg10's pgupgrade.html step 10 (upgrading standby servers)
Date: Tue, 12 Sep 2017 19:54:15 -0400
Message-ID: <20170912235415.GT4628@tamriel.snowman.net> (raw)
In-Reply-To: <VisenaEmail.6d.81d066079b42c9ec.15e787c1bfc@tc7-visena>
References: <20170912233840.GS4628@tamriel.snowman.net>
<VisenaEmail.6d.81d066079b42c9ec.15e787c1bfc@tc7-visena>
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Andreas,
* Andreas Joseph Krogh (andreas@visena.com) wrote:
> I have to ask; Why not run pg_upgrade on standby, after verifying that it's in
> sync with primary and promoting it to primary if necessary and then making it
> standby again after pg_upgrade is finished?
I don't think that we could be guaranteed that the catalog tables would
be the same on the replica as on the primary if they were actually
created by pg_upgrade.
The catalog tables *must* be identical between the primary and the
replica because they are updated subsequently through WAL replay, not
through SQL commands (which is how pg_upgrade creates them in the first
place).
Perhaps we could have some mode for pg_upgrade where it handles the
update to replicas (with the additional checks that I outlined and using
the methodology discussed for rsync --hard-links), but that would still
require solving the communicate-over-the-network problem between the
primary and the replicas, which is the hard part. Whether it's an
independent utility or something built into pg_upgrade isn't really that
big of a distinction, though it doesn't seem to me like there'd be much
code reuse there.
Thanks!
Stephen
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To: pgsql-hackers@postgresql.org
Cc: sfrost@snowman.net, andreas@visena.com, bruce@momjian.us, michael.paquier@gmail.com, robertmhaas@gmail.com
Subject: Re: Clarification in pg10's pgupgrade.html step 10 (upgrading standby servers)
In-Reply-To: <20170912235415.GT4628@tamriel.snowman.net>
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