Re: BUG #19647: Difference in pg_basebackup behaviour between PostgreSQL <= 16 and >= 17 with pgactive extension

Hi Edwin,

On Wed, Sep 2, 2026 at 1:43 PM Edwin Polkerman
<edwin(dot)polkerman(at)splendiddata(dot)com> wrote:
> Yes, the 18.6 and 17.11 global/ directory contains this file as well.
> [...]
> Because of the difference in behaviour of pg_basebackup what dazzled me, it made me decide to create the issue in the pgql-bugs mailing list. Please let me know if it is not PostgreSQL related and if it should be created in github at AWS/pgactive

It looks like the behavior change in pg_basebackup is by design [1], as of PG17.

I think that's separate from the general question of "do our checksum
tools handle arbitrary third-party files in arbitrary places", and I
think the answer to that is still "no". There was briefly some
discussion on allowing that, IIRC -- but as far as I know, it hasn't
actually been established as a supported feature? (It is clearly not
supported for PG16 and before, so I think a trip to the extension's
GitHub Issues is probably in your future either way.)

It's possible that today's pg_checksums behavior was an oversight,
because pg_checksums.c says

/*
* List of files excluded from checksum validation.
*
* Note: this list should be kept in sync with what basebackup.c
includes.
*/

and it sure seems like that list is no longer "in sync". But
personally, I don't think that's a backportable change, rather than an
enhancement request for future versions.

Thanks,
--Jacob

[1] https://postgr.es/c/025584a16