| From: | Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> |
|---|---|
| To: | Haribabu Kommi <kommi(dot)haribabu(at)gmail(dot)com> |
| Cc: | Kouhei Kaigai <kaigai(at)ak(dot)jp(dot)nec(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, Gavin Flower <GavinFlower(at)archidevsys(dot)co(dot)nz>, Jeff Davis <pgsql(at)j-davis(dot)com>, Andres Freund <andres(at)2ndquadrant(dot)com>, Amit Langote <amitlangote09(at)gmail(dot)com>, Amit Langote <Langote_Amit_f8(at)lab(dot)ntt(dot)co(dot)jp>, Fabrízio Mello <fabriziomello(at)gmail(dot)com>, Thom Brown <thom(at)linux(dot)com>, Stephen Frost <sfrost(at)snowman(dot)net>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Parallel Seq Scan |
| Date: | 2015-09-09 15:07:00 |
| Message-ID: | CAA4eK1JBu3VsJD8788k=Yt4s_CVrUx_zP9Ah-f1zAe4UAdR=6Q@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Wed, Sep 9, 2015 at 11:47 AM, Haribabu Kommi <kommi(dot)haribabu(at)gmail(dot)com>
wrote:
>
> With subquery, parallel scan is having some problem, please refer below.
>
>
> postgres=# explain analyze select * from test01 where kinkocord not in
> (select kinkocord from test02 where tenpocord = '001');
> ERROR: badly formatted node string "SUBPLAN :subLinkType 2 :testexpr"...
> CONTEXT: parallel worker, pid 32879
> postgres=#
>
The problem here is that readfuncs.c doesn't have support for reading
SubPlan nodes. I have added support for some of the nodes, but it seems
SubPlan node also needs to be added. Now I think this is okay if the
SubPlan
is any node other than Funnel, but if Subplan contains Funnel, then each
worker needs to spawn other workers to execute the Subplan which I am
not sure is the best way. Another possibility could be store the results of
Subplan in some tuplestore or some other way and then pass those to workers
which again doesn't sound to be promising way considering we might have
hashed SubPlan for which we need to build a hashtable. Yet another way
could be for such cases execute the Filter in master node only.
With Regards,
Amit Kapila.
EnterpriseDB: http://www.enterprisedb.com
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