Re: parallel mode and parallel contexts

On Thu, Dec 18, 2014 at 1:23 AM, Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
>
>
> In the meantime, I had a good chat with Heikki on IM yesterday which
> gave me some new ideas on how to fix up the transaction handling in
> here, which I am working on implementing. So hopefully I will have
> that by then.
>
> I am also hoping Amit will be adapting his parallel seq-scan patch to
> this framework.
>

While working on parallel seq-scan patch to adapt this framework, I
noticed few things and have questions regrading the same.

1.
Currently parallel worker just attaches to error queue, for tuple queue
do you expect it to be done in the same place or in the caller supplied
function, if later then we need segment address as input to that function
to attach queue to the segment(shm_mq_attach()).
Another question, I have in this regard is that if we have redirected
messages to error queue by using pq_redirect_to_shm_mq, then how can
we set tuple queue for the same purpose. Similarly I think more handling
is needed for tuple queue in master backend and the answer to above will
dictate what is the best way to do it.

2.
Currently there is no interface for wait_for_workers_to_become_ready()
in your patch, don't you think it is important that before start of fetching
tuples, we should make sure all workers are started, what if some worker
fails to start?

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