Re: PgStat_HashKey padding issue when passed by reference

Sami Imseih <samimseih@gmail.com>

From: Sami Imseih <samimseih@gmail.com>
To: Michael Paquier <michael@paquier.xyz>
Cc: Andres Freund <andres@anarazel.de>, pgsql-hackers <pgsql-hackers@postgresql.org>
Date: 2025-09-15T21:47:27Z
Lists: pgsql-hackers
> > I don't see how this improves the situation, but will just make it more
> > difficult to add a new field that requires padding in the future.
> >
> > If we are documenting either way, I rather that we just document the need
> > to pass a key by reference, which is the pattern used in other areas
> > ( see pgss_store and entry_alloc in pg_stat_statements.c )
> >
> > Others may have a different opinion.
>
> Yeah, I do care about the size of the hash key.  So if someone goes on
> and proposes the addition of a new field while we already have 8 bytes
> for the object ID, that can itself be the hash of something else
> because we area already set up for life in terms of value friction, we
> will have an interesting debate.

Just to confirm, you are saying we are unlikely to ever add a new field
to the key. Is that correct?

--
Sami Imseih
Amazon Web Services (AWS)



Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →
  1. Document and check that PgStat_HashKey has no padding