Re: Statistics Import and Export

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(at)momjian(dot)us> https://momjian.us
EDB https://enterprisedb.com

Only you can decide what is important to you.