Message-ID: <948dd810f942016c22ffe9bb4500677299553c59.camel@j-davis.com>
Subject: Re: Statistics Import and Export
From: Jeff Davis <pgsql@j-davis.com>
To: Greg Sabino Mullane <htamfids@gmail.com>
Cc: Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>, Corey Huinker
 <corey.huinker@gmail.com>, Andres Freund <andres@anarazel.de>, Tom Lane
 <tgl@sss.pgh.pa.us>, Michael Paquier <michael@paquier.xyz>, Nathan Bossart
 <nathandbossart@gmail.com>, Bruce Momjian <bruce@momjian.us>, Matthias van
 de Meent <boekewurm+postgres@gmail.com>, Magnus Hagander
 <magnus@hagander.net>, Stephen Frost <sfrost@snowman.net>, Peter Smith
 <smithpb2250@gmail.com>, PostgreSQL Hackers
 <pgsql-hackers@lists.postgresql.org>, alvherre@alvh.no-ip.org, jian he
 <jian.universality@gmail.com>
Date: Sat, 01 Mar 2025 12:48:18 -0800
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On Sat, 2025-03-01 at 13:52 -0500, Greg Sabino Mullane wrote:
> > Can you expand on some of those cases?
>=20
> Certainly. I think one of the problems is that because this patch is
> solving a pg_upgrade issue, the focus is on the "dump and restore"
> scenarios. But pg_dump is used for much more than that, especially
> "dump and examine".

Thank you for going through these examples.

> I just don't think it should be enabled by default for everything
> using pg_dump. For the record, I would not strongly object to having
> stats on by default for binary dumps, although I would prefer them
> off.

I am open to that idea, I just want to get it right, because probably
whatever the default is in 18 will stay that way.

Also, we will need to think through the set of pg_dump options again. A
lot of our tools seem to assume that "if it's the default, we don't
need a way to ask for it explicitly", which makes it a lot harder to
ever change the default and keep a coherent set of options.

> So why not just expect people to modify their programs to use --no-
> statistics for cases like this? That's certainly an option, but it's
> going to break a lot of existing things, and create branching code:

I suggest that we wait a bit to see what additional feedback we get
early in beta.

> Also, anything trained to parse pg_dump output will have to learn
> about the new SELECT pg_restore_ calls with their multi-line formats
> (not 100% sure we don't have that anywhere, as things like "SELECT
> setval" and "SELECT set_config" are single line, but there may be
> existing things)

That's an interesting point. What tools are currrently trying to parse
pg_dump output?

Regards,
	Jeff Davis