Message-ID: <af4a709627db7fa50f31e74ffd77e5376001d4ff.camel@j-davis.com>
Subject: Re: Statistics Import and Export
From: Jeff Davis <pgsql@j-davis.com>
To: Robert Treat <rob@xzilla.net>
Cc: Robert Haas <robertmhaas@gmail.com>, Andres Freund <andres@anarazel.de>,
  Corey Huinker <corey.huinker@gmail.com>, Nathan Bossart
 <nathandbossart@gmail.com>, Tom Lane <tgl@sss.pgh.pa.us>,  Michael Paquier
 <michael@paquier.xyz>, jian he <jian.universality@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>,
 Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>, Peter Smith
 <smithpb2250@gmail.com>, PostgreSQL Hackers
 <pgsql-hackers@lists.postgresql.org>, alvherre@alvh.no-ip.org
Date: Fri, 07 Mar 2025 13:43:56 -0800
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On Fri, 2025-03-07 at 15:46 -0500, Robert Treat wrote:
> There might be some variability depending on the default behavior,
> but
> if we assume that default means "output everything"

The reason I posted this patch is that, depending on performance
characteristics in v18 and a decision to be made during beta, the
default may not output statistics.

So we need whatever set of options we choose to have the freedom to
change statistics to be either opt-in or opt-out, without needing to
reconsider the overall set of options.

I tried to generalize that requirement to all of
{schema|data|statistics} for consistency, but that resulted in 9
options.

We don't need the options to be perfectly consistent at the expense of
usability, though, so if 9 options is too many we can just have three
new options for stats, for a total of 5 options:

   --data-only
   --schema-only
   --statistics-only
   --statistics (stats also, regardless of default)
   --no-statistics (no stats, regardless of default)

which would allow combinations like "--schema-only --statistics" to
mean "schema and statistics but not data". There would be a bit of
weirdness because --statistics can combine with --data-only and --
schema-only, but nothing can combine with --statistics-only.

> if you want everything --include=3Dschema,data,statistics (presumably
> redundant with the default behavior)
> if you want schema only --include=3Dschema
> if you want "everything except schema" --include=3Ddata,statistics

That could work. Comparing to the options above yields:

   --include=3Dstatistics <=3D> --statistics-only
   --include=3Dschema,data,statistics <=3D> --statistics
   --include=3Dschema,statistics <=3D> --schema-only --statistics
   --include=3Ddata,statistics <=3D> --data-only --statistics
   --include=3Dschema,data <=3D> --no-statistics

Not sure which approach is better.

Regards,
	Jeff Davis