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

Dear Amit,

> Also, what about pg_replication_origin_* APIs? Do we want to restrict
> those as well if we are restricting slot operations? I don't see any
> solid theory presented in this thread on why we should add new checks
> in multiple APIs restricting those in single-user mode.

As David [1] and documentation [2] described, single user mode is typically used
for initialization, debugging and recovery purpose - not for normal purposes.
I think doing replication stuffs is not intended. Tom also considered like that [4].

The error I reported seemed to be introduced seven years ago (0ce5cf2), and no
one has reported till now. This also implies that there are no reasons to support
it.

Ideally, functions described in [5] can be banned in the single-user mode, except
the pg_drop_replication_slot(). Thought?

[1]: https://www.postgresql.org/message-id/CAKFQuwbnBkGZAM%2B5b1DWmbqU5W7b1r-nQsw87BukrUC5WLrJXg%40mail.gmail.com
[2]: https://www.postgresql.org/docs/devel/app-postgres.html
[3]: https://www.postgresql.org/message-id/3b2f809f-326c-38dd-7a9e-897f957a4eb1%40enterprisedb.com
[4]: https://www.postgresql.org/message-id/25024.1525789919%40sss.pgh.pa.us
[5]: https://www.postgresql.org/docs/devel/functions-admin.html#FUNCTIONS-REPLICATION

Best regards,
Hayato Kuroda
FUJITSU LIMITED