From: | Robert Haas <robertmhaas(at)gmail(dot)com> |
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To: | Simon Riggs <simon(at)2ndquadrant(dot)com> |
Cc: | Kouhei Kaigai <kaigai(at)ak(dot)jp(dot)nec(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Andres Freund <andres(at)2ndquadrant(dot)com>, PgHacker <pgsql-hackers(at)postgresql(dot)org>, Stephen Frost <sfrost(at)snowman(dot)net>, Shigeru Hanada <shigeru(dot)hanada(at)gmail(dot)com>, Jim Mlodgenski <jimmy76(at)gmail(dot)com>, Peter Eisentraut <peter_e(at)gmx(dot)net>, Kohei KaiGai <kaigai(at)kaigai(dot)gr(dot)jp> |
Subject: | Re: [v9.5] Custom Plan API |
Date: | 2014-05-08 12:16:00 |
Message-ID: | CA+TgmoZFwQnjpyhBwX2P6v++ZdP-G2K_ymXHUYaR+QPpcrcp0Q@mail.gmail.com |
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Lists: | pgsql-hackers |
On Wed, May 7, 2014 at 4:01 AM, Simon Riggs <simon(at)2ndquadrant(dot)com> wrote:
> Agreed. My proposal is that if the planner allows the lookaside to an
> FDW then we pass the query for full execution on the FDW. That means
> that the scan, aggregate and join could take place via the FDW. i.e.
> "Custom Plan" == lookaside + FDW
>
> Or put another way, if we add Lookaside then we can just plug in the
> pgstrom FDW directly and we're done. And everybody else's FDW will
> work as well, so Citus etcc will not need to recode.
As Stephen notes downthread, Tom has already expressed opposition to
this idea on other threads, and I tend to agree with him, at least to
some degree. I think the drive to use foreign data wrappers for
PGStrom, CitusDB, and other things that aren't really foreign data
wrappers as originally conceived is a result of the fact that we've
got only one interface in this area that looks remotely like something
pluggable; and so everyone's trying to fit things into the constraints
of that interface whether it's actually a good fit or not.
Unfortunately, I think what CitusDB really wants is pluggable storage,
and what PGStrom really wants is custom paths, and I don't think
either of those things is the same as what FDWs provide.
--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company
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