Re: Join push-down support for foreign tables - Mailing list pgsql-hackers

Hanada-san,

Your patch mixtures enhancement of custom-/foreign-scan interface and
enhancement of contrib/postgres_fdw... Probably, it is a careless mis-
operation.
Please make your patch as differences from my infrastructure portion.


Also, I noticed this "Join pushdown support for foreign tables" patch
is unintentionally rejected in the last commit fest. https://commitfest.postgresql.org/3/20/
I couldn't register myself as reviewer. How do I operate it on the
new commitfest application?

Thanks,
--
NEC OSS Promotion Center / PG-Strom Project
KaiGai Kohei <kaigai@ak.jp.nec.com>


> -----Original Message-----
> From: pgsql-hackers-owner@postgresql.org
> [mailto:pgsql-hackers-owner@postgresql.org] On Behalf Of Shigeru Hanada
> Sent: Monday, February 16, 2015 1:03 PM
> To: Robert Haas
> Cc: PostgreSQL-development
> Subject: Re: [HACKERS] Join push-down support for foreign tables
> 
> Hi
> 
> I've revised the patch based on Kaigai-san's custom/foreign join patch
> posted in the thread below.
> 
> http://www.postgresql.org/message-id/9A28C8860F777E439AA12E8AEA7694F80
> 108C355@BPXM15GP.gisp.nec.co.jp
> 
> Basically not changed from the version in the last CF, but as Robert
> commented before, N-way (not only 2-way) joins should be supported in the
> first version by construct SELECT SQL by containing source query in FROM
> clause as inline views (a.k.a. from clause subquery).
> 
> 2014-12-26 13:48 GMT+09:00 Shigeru Hanada <shigeru.hanada@gmail.com>:
> > 2014-12-16 1:22 GMT+09:00 Robert Haas <robertmhaas@gmail.com>:
> >> On Mon, Dec 15, 2014 at 3:40 AM, Shigeru Hanada
> >> <shigeru.hanada@gmail.com> wrote:
> >>> I'm working on $SUBJECT and would like to get comments about the
> >>> design.  Attached patch is for the design below.
> >>
> >> I'm glad you are working on this.
> >>
> >>> 1. Join source relations
> >>> As described above, postgres_fdw (and most of SQL-based FDWs) needs
> >>> to check that 1) all foreign tables in the join belong to a server,
> >>> and
> >>> 2) all foreign tables have same checkAsUser.
> >>> In addition to that, I add extra limitation that both inner/outer
> >>> should be plain foreign tables, not a result of foreign join.  This
> >>> limiation makes SQL generator simple.  Fundamentally it's possible
> >>> to join even join relations, so N-way join is listed as enhancement
> >>> item below.
> >>
> >> It seems pretty important to me that we have a way to push the entire
> >> join nest down.  Being able to push down a 2-way join but not more
> >> seems like quite a severe limitation.
> >
> > Hmm, I agree to support N-way join is very useful.  Postgres-XC's SQL
> > generator seems to give us a hint for such case, I'll check it out
> > again.
> >
> > --
> > Shigeru HANADA
> 
> 
> 
> --
> Shigeru HANADA