From: Tom Lane <tgl@sss.pgh.pa.us>
To: Tomas Vondra <tomas.vondra@2ndquadrant.com>
cc: Amit Kapila <amit.kapila16@gmail.com>,
        Ian Barwick <ian.barwick@2ndquadrant.com>,
        Stephen Frost <sfrost@snowman.net>,
        Robert Haas <robertmhaas@gmail.com>,
        "pgsql-hackers@postgresql.org" <pgsql-hackers@postgresql.org>
Subject: Re: [PATCH] Stop ALTER SYSTEM from making bad assumptions
In-reply-to: <20190802222254.qsvqjtkwte464lu3@development>
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Comments: In-reply-to Tomas Vondra <tomas.vondra@2ndquadrant.com>
	message dated "Sat, 03 Aug 2019 00:22:54 +0200"
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Date: Fri, 02 Aug 2019 18:27:36 -0400
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Tomas Vondra <tomas.vondra@2ndquadrant.com> writes:
> There seems to be a consensus that this this not a pg_basebackup issue
> (i.e. duplicate values don't make the file invalid), and it should be
> handled in ALTER SYSTEM.

Yeah.  I doubt pg_basebackup is the only actor that can create such
situations.

> The proposal seems to be to run through the .auto.conf file, remove any
> duplicates, and append the new entry at the end. That seems reasonable.

+1

> There was a discussion whether to print warnings about the duplicates. I
> personally see not much point in doing that - if we consider duplicates
> to be expected, and if ALTER SYSTEM has the license to rework the config
> file any way it wants, why warn about it?

Personally I agree that warnings are unnecessary.

> The main issue however is that no code was written yet.

Seems like it ought to be relatively simple ... but I didn't look.

			regards, tom lane