Re: Minimal logical decoding on standbys

On Fri, Apr 7, 2023 at 11:42 PM Andres Freund <andres@anarazel.de> wrote:
>
> On 2023-04-07 08:47:57 -0700, Andres Freund wrote:
> > Integrated all of these.
>
> Here's my current version. Changes:
> - Integrated Bertrand's changes
> - polished commit messages of 0001-0003
> - edited code comments for 0003, including
>   InvalidateObsoleteReplicationSlots()'s header
> - added a bump of SLOT_VERSION to 0001
> - moved addition of pg_log_standby_snapshot() to 0007
> - added a catversion bump for pg_log_standby_snapshot()
> - moved all the bits dealing with procsignals from 0003 to 0004, now the split
>   makes sense IMO
> - combined a few more sucessive ->safe_psql() calls
>

The new approach for invalidation looks clean. BTW, I see minor
inconsistency in the following two error messages (errmsg):

if (MyReplicationSlot->data.invalidated == RS_INVAL_WAL)
ereport(ERROR,
(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
errmsg("can no longer get changes from replication slot \"%s\"",
NameStr(MyReplicationSlot->data.name)),
errdetail("This slot has been invalidated because it exceeded the
maximum reserved size.")));

if (MyReplicationSlot->data.invalidated != RS_INVAL_NONE)
ereport(ERROR,
(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
errmsg("cannot read from logical replication slot \"%s\"",
NameStr(MyReplicationSlot->data.name)),
errdetail("This slot has been invalidated because it was conflicting
with recovery.")));

Won't it be better to keep the same errmsg in the above two cases?

--
With Regards,
Amit Kapila.