Re: speed up a logical replica setup

On 19.03.24 08:05, Amit Kapila wrote:
> On Mon, Mar 18, 2024 at 7:22 PM Peter Eisentraut  wrote:
>>
>> In check_subscriber(): All these permissions checks seem problematic
>> to me.  We shouldn't reimplement our own copy of the server's
>> permission checks.  The server can check the permissions.  And if the
>> permission checking in the server ever changes, then we have
>> inconsistencies to take care of.  Also, the error messages "permission
>> denied" are inappropriate, because we are not doing the actual thing.
>> Maybe we want to do a dry-run for the benefit of the user, but then we
>> should do the actual thing, like try to create a replication slot, or
>> whatever.  But I would rather just remove all this, it seems too
>> problematic.
>>
> 
> If we remove all the checks then there is a possibility that we can
> fail later while creating the actual subscription. For example, if
> there are not sufficient max_replication_slots, then it is bound to
> fail in the later steps which would be a costlier affair because by
> that time the standby would have been promoted and the user won't have
> any way to move forward but to re-create standby and then use this
> tool again. I think here the patch tries to mimic pg_upgrade style
> checks where we do some pre-checks.

I think checking for required parameter settings is fine.  My concern is 
with the code before that, that does 
pg_has_role/has_database_privilege/has_function_privilege.