Date: Wed, 27 Dec 2023 22:11:23 -0500
From: Bruce Momjian <bruce@momjian.us>
To: Corey Huinker <corey.huinker@gmail.com>
Cc: Tomas Vondra <tomas.vondra@enterprisedb.com>,
	Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>,
	pgsql-hackers@lists.postgresql.org
Subject: Re: Statistics Import and Export
Message-ID: <ZYznW3RaPjGs74ix@momjian.us>
References: <CADkLM=cB0rF3p_FuWRTMSV0983ihTRpsH+OCpNyiqE7Wk0vUWA@mail.gmail.com>
 <CAExHW5uRNe856LPYH1eZFyeASv4Xs4-9d1Gqj+rzS+3StVGLxQ@mail.gmail.com>
 <CADkLM=c_iuAN19_94ikG5VeR_Z3LDkR6fKyeOz=ZKr44qweYjg@mail.gmail.com>
 <CADkLM=dTHVSrcGBAstjshoZBXKJgWjzN3Vj53KQ9fORqvkaN5Q@mail.gmail.com>
 <f0930823-d44b-21df-d718-ee3c657d9087@enterprisedb.com>
 <CADkLM=cx-XM-PTscj+uDi24x3_vDpYMOjfHgw9CFt_ad5poc0A@mail.gmail.com>
 <76596388-6fe6-0baf-351d-734458a46d76@enterprisedb.com>
 <CADkLM=frTx5DocOpyhRHL4r_LKvP315cNA-5+0UVqGM=7GKd9A@mail.gmail.com>
 <4268d862-7784-f76f-d7f1-359b0b4db67c@enterprisedb.com>
 <CADkLM=e4Uo1kTDzzUfHNzOyfz80PfJpnFurEsM7spoH9=zdrYA@mail.gmail.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <CADkLM=e4Uo1kTDzzUfHNzOyfz80PfJpnFurEsM7spoH9=zdrYA@mail.gmail.com>
Archived-At: <https://www.postgresql.org/message-id/ZYznW3RaPjGs74ix%40momjian.us>
Precedence: bulk

On Wed, Dec 27, 2023 at 09:41:31PM -0500, Corey Huinker wrote:
>     When I thought about the ability to dump/load statistics in the past, I
>     usually envisioned some sort of DDL that would do the export and import.
>     So for example we'd have EXPORT STATISTICS / IMPORT STATISTICS commands,
>     or something like that, and that'd do all the work. This would mean
>     stats are "first-class citizens" and it'd be fairly straightforward to
>     add this into pg_dump, for example. Or at least I think so ...
> 
>     Alternatively we could have the usual "functional" interface, with a
>     functions to export/import statistics, replacing the DDL commands.
> 
>     Unfortunately, none of this works for the pg_upgrade use case, because
>     existing cluster versions would not support this new interface, of
>     course. That's a significant flaw, as it'd make this useful only for
>     upgrades of future versions.
> 
> 
> This was the reason I settled on the interface that I did: while we can create
> whatever interface we want for importing the statistics, we would need to be
> able to extract stats from databases using only the facilities available in
> those same databases, and then store that in a medium that could be conveyed
> across databases, either by text files or by saving them off in a side table
> prior to upgrade. JSONB met the criteria.

Uh, it wouldn't be crazy to add this capability to pg_upgrade/pg_dump in
a minor version upgrade if it wasn't enabled by default, and if we were
very careful.

-- 
  Bruce Momjian  <bruce@momjian.us>        https://momjian.us
  EDB                                      https://enterprisedb.com

  Only you can decide what is important to you.