Subject: Test case for parameterized remote path in postgres_fdw

From: Etsuro Fujita <[email-masked]>
Date: Tue, 15 Aug 2023 20:49:59 +0900

Hi,

While working on the join pushdown issue, I noticed this bit in commit
e4106b252:

--- parameterized remote path
+-- parameterized remote path for foreign table
 EXPLAIN (VERBOSE, COSTS false)
-  SELECT * FROM ft2 a, ft2 b WHERE a.c1 = 47 AND b.c1 = a.c2;
+  SELECT * FROM "S 1"."T 1" a, ft2 b WHERE a."C 1" = 47 AND b.c1 = a.c2;
 SELECT * FROM ft2 a, ft2 b WHERE a.c1 = 47 AND b.c1 = a.c2;
+

The first statement was modified to test the intended behavior, but
the second one was not.  The second one as-is performs a foreign join:

EXPLAIN (VERBOSE, COSTS OFF)
SELECT * FROM ft2 a, ft2 b WHERE a.c1 = 47 AND b.c1 = a.c2;

                                         QUERY PLAN
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
 Foreign Scan
   Output: a.c1, a.c2, a.c3, a.c4, a.c5, a.c6, a.c7, a.c8, b.c1, b.c2,
b.c3, b.c4, b.c5, b.c6, b.c7, b.c8
   Relations: (public.ft2 a) INNER JOIN (public.ft2 b)
   Remote SQL: SELECT r1."C 1", r1.c2, r1.c3, r1.c4, r1.c5, r1.c6,
r1.c7, r1.c8, r2."C 1", r2.c2, r2.c3, r2.c4, r2.c5, r2.c6, r2.c7,
r2.c8 FROM ("S 1"."T 1" r1 INNER JOIN "S 1"."T 1" r2 ON (((r1.c2 =
r2."C 1")) AND ((r1."C 1" = 47))))
(4 rows)

So we should have modified the second one as well?  Attached is a
small patch for that.

Best regards,
Etsuro Fujita