Re: Parallel Seq Scan

On 13-03-2015 AM 10:24, Amit Kapila wrote:
> On Thu, Mar 12, 2015 at 4:22 PM, Amit Langote <Langote_Amit_f8(at)lab(dot)ntt(dot)co(dot)jp>
>> From Robert's description[1], it looked like the NestLoop with Funnel
> would
>> have Funnel as either outer plan or topmost plan node or NOT a
> parameterised
>> plan. In that case, would this case arise or am I missing something?
>>
>
> Probably not if the costing is right and user doesn't manually disable
> plans (like by set enable_* = off). However we should have rescan code
> incase it chooses the plan such that Funnel is inner node and I think
> apart from that also in few cases Rescan is required.
>

I see, thanks.

By the way, is it right that TupleQueueFunnel.queue has one shm_mq_handle per
initialized parallel worker? If so, how does TupleQueueFunnel.maxqueues relate
to ParallelContext.nworkers (of the corresponding parallel context)?

Why I asked this is because in CreateTupleQueueFunnel():

funnel->maxqueues = 8;
funnel->queue = palloc(funnel->maxqueues * sizeof(shm_mq_handle *));

So, is the hardcoded "8" intentional or an oversight?

Thanks,
Amit