Re: IF [NOT] EXISTS for replication slots

On Tue, Feb 7, 2017 at 2:07 AM, Petr Jelinek
<petr(dot)jelinek(at)2ndquadrant(dot)com> wrote:
> On 06/02/17 05:15, Michael Paquier wrote:
>> Hi all,
>>
>> Lately I have bumped into a case where it would have been useful to
>> make the difference between a failure because of a slot already
>> dropped and an internal failure of Postgres. Is there any interest for
>> support of IE and INE for CREATE and DROP_REPLICATION_SLOT?
>> My use case involved only the SQL-callable interface, but I would
>> think that it is useful to make this difference as well with the
>> replication protocol. For the function we could just add a boolean
>> argument to control the switch, and for the replication commands a
>> dedicated keyword.
>>
>> Any thoughts?
>
> My thought is, how would this handle the snapshot creation that logical
> slot does when it's created?

In what is that related to IF NOT EXISTS? If the slot does not get
created you could just return NULL to the caller to let him know that
there is something already around. The use-case I have found INE
useful involved physical slots actually.
--
Michael