RE: ReplicationSlotRelease() crashes when the instance is in the single user mode

Dear hackers,

Based on the discussion, I feel it is enough to add quick error out for SQL functions. PSA attached.

Best regards,
Hayato Kuroda
FUJITSU LIMITED

> -----Original Message-----
> From: Hayato Kuroda (Fujitsu) <kuroda.hayato@fujitsu.com>
> Sent: Tuesday, February 18, 2025 5:24 PM
> To: 'Michael Paquier' <michael@paquier.xyz>
> Cc: 'pgsql-hackers@lists.postgresql.org' <pgsql-hackers@lists.postgresql.org>
> Subject: RE: ReplicationSlotRelease() crashes when the instance is in the single
> user mode
> 
> Dear Michael,
> 
> > Ah, good point for the slot drop.  So 0ce5cf2ef24f is claiming that
> > some of these manipulations are OK.  I didn't suspect this one.
> 
> Yeah, I think so.
> 
> > Slot advancing is a very different beast, unfortunately, that may
> > depend on many other subsystems.  For example with logical slots we
> > would finish by calling rm_decode, which could be outside of core.
> > Justifying that this operation is supported in single-user mode is
> > larger than what you are suggesting here..
> 
> OK. Actually, I do not have any use-cases in my mind. I played because
> I found a special path for single user mode in ReplicationSlotAcquire()
> so that I wanted to see the behavior.
> 
> Best regards,
> Hayato Kuroda
> FUJITSU LIMITED
> 
>