Date: Fri, 8 Nov 2019 10:20:03 +0100
From: Christoph Berg <myon@debian.org>
To: Laurenz Albe <laurenz.albe@cybertec.at>
Cc: Thomas Munro <thomas.munro@gmail.com>,
	Michael Paquier <michael@paquier.xyz>,
	Julien Rouhaud <rjuju123@gmail.com>,
	Peter Eisentraut <peter.eisentraut@2ndquadrant.com>,
	Douglas Doole <dougdoole@gmail.com>,
	Pg Hackers <pgsql-hackers@postgresql.org>
Subject: Re: Collation versioning
Message-ID: <20191108092003.GA8017@msg.df7cb.de>
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	Laurenz Albe <laurenz.albe@cybertec.at>,
	Thomas Munro <thomas.munro@gmail.com>,
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	Julien Rouhaud <rjuju123@gmail.com>,
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	Douglas Doole <dougdoole@gmail.com>,
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Re: Laurenz Albe 2019-11-08 <3c3b9ff84d21acf3188558928249d04db84ea2e9.camel@cybertec.at>
> #3 is the best proposal, but there is still the need to run
> ALTER INDEX on all affected indexes to keep PostgreSQL from nagging.
> Perhaps the situation could be improved with a pg_upgrade option
> --i-know-my-indexes-are-fine that causes a result like #2.
> Together with a bold note in the release notes, this may relieve
> the pain.

Ack.

We should also try to make the actual commands more accessible.
Instead of having the user specify a version number we could as well
determine from the current state of the system as in
  ALTER INDEX ... DEPENDS ON 'version-number-I-never-heard-of-before'
could it just be
  ALTER INDEX ... COLLATION IS CURRENT
or, given the general action to take is reindexing, how about a no-op reindex?
  REINDEX INDEX ... METADATA ONLY

That might look less scary to the average end user.

Do we even think people upgrade PG and the OS at the same time?
pg_upgrade might frequently actually be invoked on an otherwise
unchanged system, so we could even make "collations are fine" the
default for pg_upgrade. And maybe have a switch like pg_upgrade --os-upgrade
that reverses this.

Christoph