Re: asynchronous execution

Hi, I've returned.

At Thu, 29 Jun 2017 14:08:27 +0900, Amit Langote <Langote_Amit_f8(at)lab(dot)ntt(dot)co(dot)jp> wrote in <63a5a01c-2967-83e0-8bbf-c981404f529e(at)lab(dot)ntt(dot)co(dot)jp>
> Hi,
>
> On 2017/06/29 13:45, Kyotaro HORIGUCHI wrote:
> > Thank you for looking this.
> >
> > At Wed, 28 Jun 2017 10:23:54 +0200, Antonin Houska wrote:
> >> Can you please explain this part of make_append() ?
> >>
> >> /* Currently async on partitioned tables is not available */
> >> Assert(nasyncplans == 0 || partitioned_rels == NIL);
> >>
> >> I don't think the output of Append plan is supposed to be ordered even if the
> >> underlying relation is partitioned. Besides ordering, is there any other
> >> reason not to use the asynchronous execution?
>
> When making an Append for a partitioned table, among the arguments passed
> to make_append(), 'partitioned_rels' is a list of RT indexes of
> partitioned tables in the inheritance tree of which the aforementioned
> partitioned table is the root. 'appendplans' is a list of subplans for
> scanning the leaf partitions in the tree. Note that the 'appendplans'
> list contains no members corresponding to the partitioned tables, because
> we don't need to scan them (only leaf relations contain any data).
>
> The point of having the 'partitioned_rels' list in the resulting Append
> plan is so that the executor can identify those relations and take the
> appropriate locks on them.

Amit, thank you for the detailed explanation. I understand what
it is and that just ignoring it is enough, then confirmed that
actually works as before.

I'll then adresss Antonin's comments tomorrow.

regards,

--
Kyotaro Horiguchi
NTT Open Source Software Center