Re: Concurrency bug in UPDATE of partition-key

On Thu, Jun 7, 2018 at 1:53 PM, Amit Khandekar <amitdkhan(dot)pg(at)gmail(dot)com> wrote:
> On 7 June 2018 at 11:44, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
>> On Tue, Jun 5, 2018 at 8:03 PM, Amit Khandekar <amitdkhan(dot)pg(at)gmail(dot)com>
>> wrote:
>>
>> I think this will allow before row delete triggers to be fired more than
>> once. Normally, if the EvalPlanQual testing generates a new tuple, we don't
>> fire the triggers again.
>
> If there are BR delete triggers, the tuple will be locked using
> GetTupleForTrigger(). So the subsequent EvalPlanQual testing won't be
> run, since the tuple is already locked due to triggers having run.
>
> But that leads me to think : The same concurrency issue can occur in
> GetTupleForTrigger() also. Say, a concurrent session has already
> locked the tuple, and GetTupleForTrigger() would wait and then return
> the updated tuple in its last parameter newSlot. In that case, we need
> to pass this slot back through ExecBRDeleteTriggers(), and further
> through epqslot parameter of ExecDelete(). But yes, in this case, we
> should avoid calling this trigger function the second time.
>
> If you agree on the above, I will send an updated patch.
>

Sounds reasonable to me.

--
With Regards,
Amit Kapila.
EnterpriseDB: http://www.enterprisedb.com