Re: [PoC] Asynchronous execution again (which is not parallel)

On Wed, Dec 2, 2015 at 7:45 AM, Kyotaro HORIGUCHI <
horiguchi(dot)kyotaro(at)lab(dot)ntt(dot)co(dot)jp> wrote:
>
> Thank you for picking this up.
>
> At Tue, 1 Dec 2015 20:33:02 +0530, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>
wrote in <CAA4eK1LBwj7heY8pxRmMCOLhuMFr81TLHck-+ByBFuUADgeu+A(at)mail(dot)gmail(dot)com
>
> > On Mon, Nov 30, 2015 at 6:17 PM, Kyotaro HORIGUCHI <
> > horiguchi(dot)kyotaro(at)lab(dot)ntt(dot)co(dot)jp> wrote:
> > > ====== TODO or random thoughts, not restricted on this patch.
> > >
> > > - This patch doesn't contain planner part, it must be aware of
> > > async execution in order that this can be in effective.
> > >
> >
> > How will you decide whether sync-execution is cheaper than parallel
> > execution. Do you have some specific cases in mind where async
> > execution will be more useful than parallel execution?
>
> Mmm.. Some confusion in wording? Sync-async is a discrimination
> about when to start execution of a node (and its
> descendents). Parallel-serial(sequential) is that of whether
> multiple nodes can execute simultaneously. Async execution
> premises parallel execution in any terms, bgworker or FDW.
>
> As I wrote in the previous mail, async execution reduces startup
> time of execution of parallel execution.
>

Could you please explain in more detail how async execution reduces
the startup time for parallel execution? Can you share the plans for
both the execution plans(with and without async execution), that might
help to understand the reason for same?

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