Re: DROP SUBSCRIPTION hangs if sub is disabled in the same transaction

On Sun, Sep 17, 2017 at 2:01 AM, Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com> wrote:
> On Sat, Sep 16, 2017 at 9:52 PM, Peter Eisentraut
> <peter(dot)eisentraut(at)2ndquadrant(dot)com> wrote:
>> On 9/15/17 13:35, Arseny Sher wrote:
>>> Peter Eisentraut <peter(dot)eisentraut(at)2ndquadrant(dot)com> writes:
>>>
>>>> Here is a simple patch that fixes this, based on my original proposal
>>>> point #4.
>>>
>>> I checked, it passes the tests and solves the problem. However, isn't
>>> this
>>>
>>> + if (slotname || !subenabled)
>>>
>>> is a truism? Is it possible that subscription has no slot but still
>>> enabled?
>>
>> Yeah, we could just remove the _at_commit() branch entirely. That would
>> effectively undo the change in 7e174fa793a2df89fe03d002a5087ef67abcdde8,
>> but I don't see any other choice for now. And the practical impact
>> would be quite limited.
>>
>
> Yeah, we can remove only _at_commit() branch, but other part of the
> commit is still valid for ALTER SUBSCRIPTION DISABLE.
>
>>> Besides, we can avoid stopping the workers if subscription has no
>>> associated replication origin, though this probably means that
>>> subscription was broken by user and is not worth it.
>>
>> Right, it seems not worth addressing this case separately.
>>
>
> Once we got this patch, DROP SUBSCRIPTION is not transactional either
> if dropping a replication slot or if the subscription got disabled in
> a transaction block. But we disallow to do DROP SUBSCRIPTION in a
> transaction block only in the former case. In the latter case, we
> adopted such non-transactional behaviour. Since these behaviours would
> be complex for users I attached the documentation patch explaining it.
>

Hmm, isn't there necessary to care and mention about this kind of
inconsistent behavior in docs?

Regards,

--
Masahiko Sawada
NIPPON TELEGRAPH AND TELEPHONE CORPORATION
NTT Open Source Software Center