On 2016/02/04 21:42, Ashutosh Bapat wrote:
* Is it safe to replace outerjoinpath with its fdw_outerpath the
following way? I think that if the join relation represented by
outerjoinpath has local conditions that can't be executed remotely,
we have to keep outerjoinpath in the path tree; we will otherwise
fail to execute the local conditions. No?
+ /*
+ * If either inner or outer path is a
ForeignPath corresponding to
+ * a pushed down join, replace it with the
fdw_outerpath, so that we
+ * maintain path for EPQ checks built
entirely of local join
+ * strategies.
+ */
+ if (IsA(joinpath->outerjoinpath, ForeignPath))
+ {
+ ForeignPath *foreign_path;
+ foreign_path = (ForeignPath
*)joinpath->outerjoinpath;
+ if
(foreign_path->path.parent->reloptkind == RELOPT_JOINREL)
+ joinpath->outerjoinpath =
foreign_path->fdw_outerpath;
+ }
all the conditions (local and remote) should be part of fdw_outerpath as
well, since that's the alternate local path, which should produce (when
converted to the plan) the same result as the foreign path.
fdw_outerpath should be a local path set when paths for
outerjoinpath->parent was being created. Am I missing something?
I assumed by mistake that only the remote conditions were evaluated in a
plan created from each fdw_outerpath. Sorry for that. I think that is
a good idea!
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).
Best regards,
Etsuro Fujita
[1]
http://www.postgresql.org/message-id/ca+tgmoba4mskgquicgt5ckbpqj-tmpqefht_wy49ndwa91w...@mail.gmail.com
*** a/contrib/postgres_fdw/postgres_fdw.c
--- b/contrib/postgres_fdw/postgres_fdw.c
***************
*** 1067,1072 **** postgresGetForeignPlan(PlannerInfo *root,
--- 1067,1076 ----
/* Build the list of columns to be fetched from the foreign server. */
fdw_scan_tlist = build_tlist_to_deparse(foreignrel);
+
+ /* Replace the targetlist of outer_plan with fdw_scan_tlist, if any */
+ if (outer_plan)
+ outer_plan->targetlist = fdw_scan_tlist;
}
/*
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