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/9a28c8860f777e439aa12e8aea7694f80108c...@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.han...@gmail.com>: > 2014-12-16 1:22 GMT+09:00 Robert Haas <robertmh...@gmail.com>: >> On Mon, Dec 15, 2014 at 3:40 AM, Shigeru Hanada >> <shigeru.han...@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
foreign_join.patch
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