Date: Wed, 14 Aug 2019 17:15:20 -0400
From: Stephen Frost <sfrost@snowman.net>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Ian Barwick <ian.barwick@2ndquadrant.com>,
	Robert Haas <robertmhaas@gmail.com>,
	Tomas Vondra <tomas.vondra@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: <20190814211520.GK16436@tamriel.snowman.net>
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Greetings,

* Tom Lane (tgl@sss.pgh.pa.us) wrote:
> Stephen Frost <sfrost@snowman.net> writes:
> > * Tom Lane (tgl@sss.pgh.pa.us) wrote:
> >> Perhaps we could put some of these details into the Notes section of t=
he
> >> ALTER SYSTEM ref page.  But I wonder how much of this is needed at all.
>=20
> > I'd be alright with that too, but I'd be just as fine with even a README
> > or something that we feel other hackers and external tool developers
> > would be likely to find.  I agree that all of this isn't something that
> > your run-of-the-mill DBA needs to know, but they are things that I'm
> > sure external tool authors will care about (including myself, David S,
> > probably the other backup/restore tool maintainers, and at least the
> > author of pg_conftool, presumably).
>=20
> In hopes of moving this along, I've pushed Ian's last code change,
> as there seems to be no real argument about that anymore.
>=20
> As for the doc changes, how about the attached revision of what
> I wrote previously?  It gives some passing mention to what ALTER
> SYSTEM will do, without belaboring it or going into things that
> are really implementation details.

It's certainly better than what we have now.

> As an example of the sort of implementation detail that I *don't*
> want to document, I invite you to experiment with the difference
> between
> 	ALTER SYSTEM SET TimeZone =3D 'America/New_York';
> 	ALTER SYSTEM SET "TimeZone" =3D 'America/New_York';

Implementation details and file formats / acceptable transformations
are naturally different things- a given implementation may sort things
one way or another but if there's no requirement that the file be sorted
then that's just fine and can be an implementation detail possibly based
around how duplicates are dealt with.

Thanks,

Stephen

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