On 2 March 2015 at 12:48, Shigeru Hanada <shigeru.han...@gmail.com> wrote:
> Attached is the revised/rebased version of the $SUBJECT. > > This patch is based on Kaigai-san's custom/foreign join patch, so > please apply it before this patch. In this version I changed some > points from original postgres_fdw. > > 1) Disabled SELECT clause optimization > ~9.4 postgres_fdw lists only columns actually used in SELECT clause, > but AFAIS it makes SQL generation complex. So I disabled such > optimization and put "NULL" for unnecessary columns in SELECT clause > of remote query. > > 2) Extended deparse context > To allow deparsing based on multiple source relations, I added some > members to context structure. They are unnecessary for simple query > with single foreign table, but IMO it should be integrated. > > With Kaigai-san's advise, changes for supporting foreign join on > postgres_fdw is minimized into postgres_fdw itself. But I added new > FDW API named GetForeignJoinPaths() to keep the policy that all > interface between core and FDW should be in FdwRoutine, instead of > using hook function. Now I'm writing document about it, and will post > it in a day. > I seem to be getting a problem with whole-row references: # SELECT p.name, c.country, e.pet_name, p FROM pets e INNER JOIN people p on e.person_id = p.id inner join countries c on p.country_id = c.id; ERROR: table "r" has 3 columns available but 4 columns specified CONTEXT: Remote SQL command: SELECT r.a_0, r.a_1, r.a_2, l.a_1 FROM (SELECT id, country FROM public.countries) l (a_0, a_1) INNER JOIN (SELECT id, name, country_id FROM public.people) r (a_0, a_1, a_2, a_3) ON ((r.a_3 = l.a_0)) And the error message could be somewhat confusing. This mentions table "r", but there's no such table or alias in my actual query. Another issue: # EXPLAIN VERBOSE SELECT NULL FROM (SELECT people.id FROM people INNER JOIN countries ON people.country_id = countries.id LIMIT 3) x; ERROR: could not open relation with OID 0 -- Thom
