From: | Robert Haas <robertmhaas(at)gmail(dot)com> |
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To: | Shigeru Hanada <shigeru(dot)hanada(at)gmail(dot)com> |
Cc: | PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: Join push-down support for foreign tables |
Date: | 2014-12-15 16:22:10 |
Message-ID: | CA+TgmoZX1Qu9MowEgMG6BzppavbNoThfOHic4Z9cRiFZKRsMjw@mail.gmail.com |
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On Mon, Dec 15, 2014 at 3:40 AM, Shigeru Hanada
<shigeru(dot)hanada(at)gmail(dot)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.
--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company
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