Re: asynchronous execution

Hello,

I'm not sure this is in a sutable shape for commit fest but I
decided to register this to ride on the bus for 10.0.

> Hi, this is the 7th patch to make instrumentation work.

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 nodesregister its async-capable children and sync and data
transferaredone out of band of ordinary ExecProcNode channel. So asyncexecution no longer disturbs async-unaware node
andslows themdown.
 

0002-Fix-some-bugs.patch
Some fixes for 0001 to work. This is just to preserve the shapeof 0001 patch.

0003-Modify-async-execution-infrastructure.patch
The original infrastructure doesn't work when multiple foreigntables 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 ofbranches. This fixes it by using unlikely() macro.

0007-Add-instrumentation-to-async-execution.patch
As the description above for 0001, async infrastructure conveystuples outside ExecProcNode channel so EXPLAIN ANALYZE
requiresspecialtreat 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

regards,

-- 
Kyotaro Horiguchi
NTT Open Source Software Center