Re: asynchronous execution

This patch conflicts with e13029a (es_query_dsa) so I rebased
this.

At Mon, 31 Oct 2016 10:39:12 +0900 (JST), Kyotaro HORIGUCHI <horiguchi(dot)kyotaro(at)lab(dot)ntt(dot)co(dot)jp> wrote in <20161031(dot)103912(dot)217430542(dot)horiguchi(dot)kyotaro(at)lab(dot)ntt(dot)co(dot)jp>
> This a PoC patch of asynchronous execution feature, based on a
> executor infrastructure Robert proposed. These patches are
> rebased on the current master.
>
> 0001-robert-s-2nd-framework.patch
>
> Roberts executor async infrastructure. Async-driver nodes
> register its async-capable children and sync and data transfer
> are done out of band of ordinary ExecProcNode channel. So async
> execution no longer disturbs async-unaware node and slows them
> down.
>
> 0002-Fix-some-bugs.patch
>
> Some fixes for 0001 to work. This is just to preserve the shape
> of 0001 patch.
>
> 0003-Modify-async-execution-infrastructure.patch
>
> The original infrastructure doesn't work when multiple foreign
> tables is on the same connection. This makes it work.
>
> 0004-Make-postgres_fdw-async-capable.patch
>
> Makes postgres_fdw to work asynchronously.
>
> 0005-Use-resource-owner-to-prevent-wait-event-set-from-le.patch
>
> This addresses a problem pointed by Robers about 0001 patch,
> that WaitEventSet used for async execution can leak by errors.
>
> 0006-Apply-unlikely-to-suggest-synchronous-route-of-ExecA.patch
>
> ExecAppend gets a bit slower by penalties of misprediction of
> branches. This fixes it by using unlikely() macro.
>
> 0007-Add-instrumentation-to-async-execution.patch
>
> As the description above for 0001, async infrastructure conveys
> tuples outside ExecProcNode channel so EXPLAIN ANALYZE requires
> special treat to show sane results. This patch tries that.
>
>
> A result of a performance measurement is in this message.
>
> https://www.postgresql.org/message-id/20161025.182150.230901487.horiguchi.kyotaro@lab.ntt.co.jp
>
>
> | t0 - SELECT sum(a) FROM <local single table>;
> | pl - SELECT sum(a) FROM <4 local children>;
> | pf0 - SELECT sum(a) FROM <4 foreign children on single connection>;
> | pf1 - SELECT sum(a) FROM <4 foreign children on dedicate connections>;
> ...
> | async
> | t0: 3885.84 ( 40.20) 0.86% faster (should be error but stable on my env..)
> | pl: 1617.20 ( 3.51) 1.26% faster (ditto)
> | pf0: 6680.95 (478.72) 19.5% faster
> | pf1: 1886.87 ( 36.25) 77.1% faster

--
Kyotaro Horiguchi
NTT Open Source Software Center