| From: | Ashutosh Bapat <ashutosh(dot)bapat(at)enterprisedb(dot)com> |
|---|---|
| To: | Etsuro Fujita <fujita(dot)etsuro(at)lab(dot)ntt(dot)co(dot)jp> |
| Cc: | Robert Haas <robertmhaas(at)gmail(dot)com>, Thom Brown <thom(at)linux(dot)com>, "pgsql-hackers(at)postgreSQL(dot)org" <pgsql-hackers(at)postgresql(dot)org>, Kouhei Kaigai <kaigai(at)ak(dot)jp(dot)nec(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Shigeru Hanada <shigeru(dot)hanada(at)gmail(dot)com> |
| Subject: | Re: postgres_fdw join pushdown (was Re: Custom/Foreign-Join-APIs) |
| Date: | 2016-02-05 08:50:00 |
| Message-ID: | CAFjFpReinb4qJ+EkPZmt7sOATfvjA=UEeFxv0wF5b1Uzan51WQ@mail.gmail.com |
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| Lists: | pgsql-hackers |
> Btw, IIUC, I think the patch fails to adjust the targetlist of the top
> plan created that way, to output the fdw_scan_tlist, as discussed in [1]
> (ie, I think the attached patch is needed, which is created on top of your
> patch pg_fdw_join_v8.patch).
>
>
fdw_scan_tlist represents the output fetched from the foreign server and is
not necessarily the output of ForeignScan. ForeignScan node's output is
represented by tlist argument to.
1119 return make_foreignscan(tlist,
1120 local_exprs,
1121 scan_relid,
1122 params_list,
1123 fdw_private,
1124 fdw_scan_tlist,
1125 remote_exprs,
1126 outer_plan);
This tlist is built using build_path_tlist() for all join plans. IIUC, all
of them output the same targetlist. We don't need to make sure that
targetlist match as long as we are using the targetlist passed in by
create_scan_plan(). Do you have a counter example?
--
Best Wishes,
Ashutosh Bapat
EnterpriseDB Corporation
The Postgres Database Company
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