Re: [HACKERS] Enabling parallelism for queries coming from SQL orother PL functions - Mailing list pgsql-hackers

On Tue, Mar 21, 2017 at 6:36 AM, Dilip Kumar <dilipbalaut@gmail.com> wrote:
> On Tue, Mar 21, 2017 at 3:36 PM, Rafia Sabih
> <rafia.sabih@enterprisedb.com> wrote:
>> On Wed, Mar 15, 2017 at 8:55 PM, Robert Haas <robertmhaas@gmail.com> wrote:
>>> Note this:
>>>
>>>         if (completed || !fcache->returnsSet)
>>>             postquel_end(es);
>>>
>>> When the SQL function doesn't return a set, then we can allow
>>> parallelism even when lazyEval is set, because we'll only call
>>> ExecutorStart() once.  But my impression is that something like this:
>
> How about taking the decision of execute_once based on
> fcache->returnsSet instead of based on lazyEval?
>
> change
> + ExecutorRun(es->qd, ForwardScanDirection, count, !es->lazyEval);
> to
> + ExecutorRun(es->qd, ForwardScanDirection, count, !fcache->returnsSet);
>
> IMHO, Robert have the same thing in mind?

Yeah, something like that.

>>SELECT * FROM blah() LIMIT 3
>>
>>...will trigger three separate calls to ExecutorRun(), which is a
>>problem if the plan is a parallel plan.
>
> And you also need to test this case what Robert have mentioned up thread.

+1

-- 
Robert Haas
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