Date: Mon, 24 Jun 2019 14:56:47 -0400
From: Stephen Frost <sfrost@snowman.net>
To: Robert Haas <robertmhaas@gmail.com>
Cc: Tom Lane <tgl@sss.pgh.pa.us>, Ian Barwick <ian.barwick@2ndquadrant.com>,
	Amit Kapila <amit.kapila16@gmail.com>,
	"pgsql-hackers@postgresql.org" <pgsql-hackers@postgresql.org>
Subject: Re: [PATCH] Stop ALTER SYSTEM from making bad assumptions
Message-ID: <20190624185647.GW2480@tamriel.snowman.net>
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Greetings,

* Robert Haas (robertmhaas@gmail.com) wrote:
> On Fri, Jun 21, 2019 at 12:55 PM Tom Lane <tgl@sss.pgh.pa.us> wrote:
> > Ah, got it.  So it seems like the correct behavior might be for
> > ALTER SYSTEM to
> > (a) run through the whole file and remove any conflicting lines;
> > (b) append new setting at the end.
>=20
> That is exactly the behavior for which I am arguing.  Stephen also
> wants a warning, but I disagree, because the warning is totally
> non-actionable.  It tells you that some tool, at some point in the
> past, did something bad. You can't do anything about that, and you
> wouldn't need to except for the arbitrary decision to label duplicate
> lines as bad in the first place.

Stephen and Magnus want a warning, because it's an indication that a
tool author, or *something* modified the file in an unexpected way, and
that we are having to do some kind of cleanup on the file because of it.

If it was a tool author, who it certainly may very well be as they're
writing in support for the v12 changes, they'd almost certainly go and
fix their code to avoid doing that, lest users complain, which would be
exactly the behavior we want.

If it was the user themselves, which is also *entirely* likely, then
hopefully they'd realize that they really shouldn't be modifying that
file.

Thanks,

Stephen

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