On 2017/01/05 12:10, Etsuro Fujita wrote:
On 2016/12/28 17:34, Ashutosh Bapat wrote:
Hmm. If I understand the patch correctly, it does not return any path
when merge join is allowed and there are merge clauses but no hash
clauses. In this case we will not create a foreign join path, loosing
some optimization. If we remove GetExistingLocalJoinPath, which
returns a path in those cases as well, we have a regression in
performance.


Ok, will revise, but as I mentioned upthread, I'm not sure it's a good
idea to search the pathlist to get a merge join even in this case.  I'd
vote for creating a merge join path from the inner/outer paths in this
case as well.

Done.  Attached is the new version of the patch.

* I'm still not sure the search approach is the right way to go, so I modified CreateLocalJoinPath so that it creates a mergejoin path that explicitly sorts both the outer and inner relations as in sort_inner_and_outer, by using the information saved in that function. I think we could try to create a sort-free mergejoin as in match_unsorted_outer, but I'm not sure it's worth complicating the code. * I modified CreateLocalJoinPath so that it handles the cheapest-total paths for the outer/inner relations that are parameterized if possible.
* I adjusted the code and revised some comments.

As I said upthread, we could skip costing for a local join path in CreateLocalJoinPath, for efficiency, but I'm not sure we should do that.

Best regards,
Etsuro Fujita
*** a/contrib/postgres_fdw/expected/postgres_fdw.out
--- b/contrib/postgres_fdw/expected/postgres_fdw.out
***************
*** 1519,1540 **** SELECT t1.c1, t2.c1 FROM ft1 t1 JOIN ft2 t2 ON (t1.c1 = t2.c1) ORDER BY t1.c3, t
                 Output: t1.c1, t2.c1, t1.c3, t1.*, t2.*
                 Relations: (public.ft1 t1) INNER JOIN (public.ft2 t2)
                 Remote SQL: SELECT r1."C 1", r1.c3, CASE WHEN (r1.*)::text IS NOT NULL THEN ROW(r1."C 1", r1.c2, r1.c3, r1.c4, r1.c5, r1.c6, r1.c7, r1.c8) END, r2."C 1", CASE WHEN (r2.*)::text IS NOT NULL THEN ROW(r2."C 1", r2.c2, r2.c3, r2.c4, r2.c5, r2.c6, r2.c7, r2.c8) END FROM ("S 1"."T 1" r1 INNER JOIN "S 1"."T 1" r2 ON (((r1."C 1" = r2."C 1")))) ORDER BY r1.c3 ASC NULLS LAST, r1."C 1" ASC NULLS LAST FOR UPDATE OF r1
!                ->  Merge Join
                       Output: t1.c1, t1.c3, t1.*, t2.c1, t2.*
!                      Merge Cond: (t1.c1 = t2.c1)
!                      ->  Sort
                             Output: t1.c1, t1.c3, t1.*
!                            Sort Key: t1.c1
!                            ->  Foreign Scan on public.ft1 t1
!                                  Output: t1.c1, t1.c3, t1.*
!                                  Remote SQL: SELECT "C 1", c2, c3, c4, c5, c6, c7, c8 FROM "S 1"."T 1" FOR UPDATE
!                      ->  Sort
                             Output: t2.c1, t2.*
!                            Sort Key: t2.c1
!                            ->  Foreign Scan on public.ft2 t2
!                                  Output: t2.c1, t2.*
!                                  Remote SQL: SELECT "C 1", c2, c3, c4, c5, c6, c7, c8 FROM "S 1"."T 1"
! (23 rows)
  
  SELECT t1.c1, t2.c1 FROM ft1 t1 JOIN ft2 t2 ON (t1.c1 = t2.c1) ORDER BY t1.c3, t1.c1 OFFSET 100 LIMIT 10 FOR UPDATE OF t1;
   c1  | c1  
--- 1519,1534 ----
                 Output: t1.c1, t2.c1, t1.c3, t1.*, t2.*
                 Relations: (public.ft1 t1) INNER JOIN (public.ft2 t2)
                 Remote SQL: SELECT r1."C 1", r1.c3, CASE WHEN (r1.*)::text IS NOT NULL THEN ROW(r1."C 1", r1.c2, r1.c3, r1.c4, r1.c5, r1.c6, r1.c7, r1.c8) END, r2."C 1", CASE WHEN (r2.*)::text IS NOT NULL THEN ROW(r2."C 1", r2.c2, r2.c3, r2.c4, r2.c5, r2.c6, r2.c7, r2.c8) END FROM ("S 1"."T 1" r1 INNER JOIN "S 1"."T 1" r2 ON (((r1."C 1" = r2."C 1")))) ORDER BY r1.c3 ASC NULLS LAST, r1."C 1" ASC NULLS LAST FOR UPDATE OF r1
!                ->  Nested Loop
                       Output: t1.c1, t1.c3, t1.*, t2.c1, t2.*
!                      Join Filter: (t1.c1 = t2.c1)
!                      ->  Foreign Scan on public.ft1 t1
                             Output: t1.c1, t1.c3, t1.*
!                            Remote SQL: SELECT "C 1", c2, c3, c4, c5, c6, c7, c8 FROM "S 1"."T 1" FOR UPDATE
!                      ->  Foreign Scan on public.ft2 t2
                             Output: t2.c1, t2.*
!                            Remote SQL: SELECT "C 1", c2, c3, c4, c5, c6, c7, c8 FROM "S 1"."T 1"
! (17 rows)
  
  SELECT t1.c1, t2.c1 FROM ft1 t1 JOIN ft2 t2 ON (t1.c1 = t2.c1) ORDER BY t1.c3, t1.c1 OFFSET 100 LIMIT 10 FOR UPDATE OF t1;
   c1  | c1  
***************
*** 1563,1584 **** SELECT t1.c1, t2.c1 FROM ft1 t1 JOIN ft2 t2 ON (t1.c1 = t2.c1) ORDER BY t1.c3, t
                 Output: t1.c1, t2.c1, t1.c3, t1.*, t2.*
                 Relations: (public.ft1 t1) INNER JOIN (public.ft2 t2)
                 Remote SQL: SELECT r1."C 1", r1.c3, CASE WHEN (r1.*)::text IS NOT NULL THEN ROW(r1."C 1", r1.c2, r1.c3, r1.c4, r1.c5, r1.c6, r1.c7, r1.c8) END, r2."C 1", CASE WHEN (r2.*)::text IS NOT NULL THEN ROW(r2."C 1", r2.c2, r2.c3, r2.c4, r2.c5, r2.c6, r2.c7, r2.c8) END FROM ("S 1"."T 1" r1 INNER JOIN "S 1"."T 1" r2 ON (((r1."C 1" = r2."C 1")))) ORDER BY r1.c3 ASC NULLS LAST, r1."C 1" ASC NULLS LAST FOR UPDATE OF r1 FOR UPDATE OF r2
!                ->  Merge Join
                       Output: t1.c1, t1.c3, t1.*, t2.c1, t2.*
!                      Merge Cond: (t1.c1 = t2.c1)
!                      ->  Sort
                             Output: t1.c1, t1.c3, t1.*
!                            Sort Key: t1.c1
!                            ->  Foreign Scan on public.ft1 t1
!                                  Output: t1.c1, t1.c3, t1.*
!                                  Remote SQL: SELECT "C 1", c2, c3, c4, c5, c6, c7, c8 FROM "S 1"."T 1" FOR UPDATE
!                      ->  Sort
                             Output: t2.c1, t2.*
!                            Sort Key: t2.c1
!                            ->  Foreign Scan on public.ft2 t2
!                                  Output: t2.c1, t2.*
!                                  Remote SQL: SELECT "C 1", c2, c3, c4, c5, c6, c7, c8 FROM "S 1"."T 1" FOR UPDATE
! (23 rows)
  
  SELECT t1.c1, t2.c1 FROM ft1 t1 JOIN ft2 t2 ON (t1.c1 = t2.c1) ORDER BY t1.c3, t1.c1 OFFSET 100 LIMIT 10 FOR UPDATE;
   c1  | c1  
--- 1557,1572 ----
                 Output: t1.c1, t2.c1, t1.c3, t1.*, t2.*
                 Relations: (public.ft1 t1) INNER JOIN (public.ft2 t2)
                 Remote SQL: SELECT r1."C 1", r1.c3, CASE WHEN (r1.*)::text IS NOT NULL THEN ROW(r1."C 1", r1.c2, r1.c3, r1.c4, r1.c5, r1.c6, r1.c7, r1.c8) END, r2."C 1", CASE WHEN (r2.*)::text IS NOT NULL THEN ROW(r2."C 1", r2.c2, r2.c3, r2.c4, r2.c5, r2.c6, r2.c7, r2.c8) END FROM ("S 1"."T 1" r1 INNER JOIN "S 1"."T 1" r2 ON (((r1."C 1" = r2."C 1")))) ORDER BY r1.c3 ASC NULLS LAST, r1."C 1" ASC NULLS LAST FOR UPDATE OF r1 FOR UPDATE OF r2
!                ->  Nested Loop
                       Output: t1.c1, t1.c3, t1.*, t2.c1, t2.*
!                      Join Filter: (t1.c1 = t2.c1)
!                      ->  Foreign Scan on public.ft1 t1
                             Output: t1.c1, t1.c3, t1.*
!                            Remote SQL: SELECT "C 1", c2, c3, c4, c5, c6, c7, c8 FROM "S 1"."T 1" FOR UPDATE
!                      ->  Foreign Scan on public.ft2 t2
                             Output: t2.c1, t2.*
!                            Remote SQL: SELECT "C 1", c2, c3, c4, c5, c6, c7, c8 FROM "S 1"."T 1" FOR UPDATE
! (17 rows)
  
  SELECT t1.c1, t2.c1 FROM ft1 t1 JOIN ft2 t2 ON (t1.c1 = t2.c1) ORDER BY t1.c3, t1.c1 OFFSET 100 LIMIT 10 FOR UPDATE;
   c1  | c1  
***************
*** 1608,1629 **** SELECT t1.c1, t2.c1 FROM ft1 t1 JOIN ft2 t2 ON (t1.c1 = t2.c1) ORDER BY t1.c3, t
                 Output: t1.c1, t2.c1, t1.c3, t1.*, t2.*
                 Relations: (public.ft1 t1) INNER JOIN (public.ft2 t2)
                 Remote SQL: SELECT r1."C 1", r1.c3, CASE WHEN (r1.*)::text IS NOT NULL THEN ROW(r1."C 1", r1.c2, r1.c3, r1.c4, r1.c5, r1.c6, r1.c7, r1.c8) END, r2."C 1", CASE WHEN (r2.*)::text IS NOT NULL THEN ROW(r2."C 1", r2.c2, r2.c3, r2.c4, r2.c5, r2.c6, r2.c7, r2.c8) END FROM ("S 1"."T 1" r1 INNER JOIN "S 1"."T 1" r2 ON (((r1."C 1" = r2."C 1")))) ORDER BY r1.c3 ASC NULLS LAST, r1."C 1" ASC NULLS LAST FOR SHARE OF r1
!                ->  Merge Join
                       Output: t1.c1, t1.c3, t1.*, t2.c1, t2.*
!                      Merge Cond: (t1.c1 = t2.c1)
!                      ->  Sort
                             Output: t1.c1, t1.c3, t1.*
!                            Sort Key: t1.c1
!                            ->  Foreign Scan on public.ft1 t1
!                                  Output: t1.c1, t1.c3, t1.*
!                                  Remote SQL: SELECT "C 1", c2, c3, c4, c5, c6, c7, c8 FROM "S 1"."T 1" FOR SHARE
!                      ->  Sort
                             Output: t2.c1, t2.*
!                            Sort Key: t2.c1
!                            ->  Foreign Scan on public.ft2 t2
!                                  Output: t2.c1, t2.*
!                                  Remote SQL: SELECT "C 1", c2, c3, c4, c5, c6, c7, c8 FROM "S 1"."T 1"
! (23 rows)
  
  SELECT t1.c1, t2.c1 FROM ft1 t1 JOIN ft2 t2 ON (t1.c1 = t2.c1) ORDER BY t1.c3, t1.c1 OFFSET 100 LIMIT 10 FOR SHARE OF t1;
   c1  | c1  
--- 1596,1611 ----
                 Output: t1.c1, t2.c1, t1.c3, t1.*, t2.*
                 Relations: (public.ft1 t1) INNER JOIN (public.ft2 t2)
                 Remote SQL: SELECT r1."C 1", r1.c3, CASE WHEN (r1.*)::text IS NOT NULL THEN ROW(r1."C 1", r1.c2, r1.c3, r1.c4, r1.c5, r1.c6, r1.c7, r1.c8) END, r2."C 1", CASE WHEN (r2.*)::text IS NOT NULL THEN ROW(r2."C 1", r2.c2, r2.c3, r2.c4, r2.c5, r2.c6, r2.c7, r2.c8) END FROM ("S 1"."T 1" r1 INNER JOIN "S 1"."T 1" r2 ON (((r1."C 1" = r2."C 1")))) ORDER BY r1.c3 ASC NULLS LAST, r1."C 1" ASC NULLS LAST FOR SHARE OF r1
!                ->  Nested Loop
                       Output: t1.c1, t1.c3, t1.*, t2.c1, t2.*
!                      Join Filter: (t1.c1 = t2.c1)
!                      ->  Foreign Scan on public.ft1 t1
                             Output: t1.c1, t1.c3, t1.*
!                            Remote SQL: SELECT "C 1", c2, c3, c4, c5, c6, c7, c8 FROM "S 1"."T 1" FOR SHARE
!                      ->  Foreign Scan on public.ft2 t2
                             Output: t2.c1, t2.*
!                            Remote SQL: SELECT "C 1", c2, c3, c4, c5, c6, c7, c8 FROM "S 1"."T 1"
! (17 rows)
  
  SELECT t1.c1, t2.c1 FROM ft1 t1 JOIN ft2 t2 ON (t1.c1 = t2.c1) ORDER BY t1.c3, t1.c1 OFFSET 100 LIMIT 10 FOR SHARE OF t1;
   c1  | c1  
***************
*** 1652,1673 **** SELECT t1.c1, t2.c1 FROM ft1 t1 JOIN ft2 t2 ON (t1.c1 = t2.c1) ORDER BY t1.c3, t
                 Output: t1.c1, t2.c1, t1.c3, t1.*, t2.*
                 Relations: (public.ft1 t1) INNER JOIN (public.ft2 t2)
                 Remote SQL: SELECT r1."C 1", r1.c3, CASE WHEN (r1.*)::text IS NOT NULL THEN ROW(r1."C 1", r1.c2, r1.c3, r1.c4, r1.c5, r1.c6, r1.c7, r1.c8) END, r2."C 1", CASE WHEN (r2.*)::text IS NOT NULL THEN ROW(r2."C 1", r2.c2, r2.c3, r2.c4, r2.c5, r2.c6, r2.c7, r2.c8) END FROM ("S 1"."T 1" r1 INNER JOIN "S 1"."T 1" r2 ON (((r1."C 1" = r2."C 1")))) ORDER BY r1.c3 ASC NULLS LAST, r1."C 1" ASC NULLS LAST FOR SHARE OF r1 FOR SHARE OF r2
!                ->  Merge Join
                       Output: t1.c1, t1.c3, t1.*, t2.c1, t2.*
!                      Merge Cond: (t1.c1 = t2.c1)
!                      ->  Sort
                             Output: t1.c1, t1.c3, t1.*
!                            Sort Key: t1.c1
!                            ->  Foreign Scan on public.ft1 t1
!                                  Output: t1.c1, t1.c3, t1.*
!                                  Remote SQL: SELECT "C 1", c2, c3, c4, c5, c6, c7, c8 FROM "S 1"."T 1" FOR SHARE
!                      ->  Sort
                             Output: t2.c1, t2.*
!                            Sort Key: t2.c1
!                            ->  Foreign Scan on public.ft2 t2
!                                  Output: t2.c1, t2.*
!                                  Remote SQL: SELECT "C 1", c2, c3, c4, c5, c6, c7, c8 FROM "S 1"."T 1" FOR SHARE
! (23 rows)
  
  SELECT t1.c1, t2.c1 FROM ft1 t1 JOIN ft2 t2 ON (t1.c1 = t2.c1) ORDER BY t1.c3, t1.c1 OFFSET 100 LIMIT 10 FOR SHARE;
   c1  | c1  
--- 1634,1649 ----
                 Output: t1.c1, t2.c1, t1.c3, t1.*, t2.*
                 Relations: (public.ft1 t1) INNER JOIN (public.ft2 t2)
                 Remote SQL: SELECT r1."C 1", r1.c3, CASE WHEN (r1.*)::text IS NOT NULL THEN ROW(r1."C 1", r1.c2, r1.c3, r1.c4, r1.c5, r1.c6, r1.c7, r1.c8) END, r2."C 1", CASE WHEN (r2.*)::text IS NOT NULL THEN ROW(r2."C 1", r2.c2, r2.c3, r2.c4, r2.c5, r2.c6, r2.c7, r2.c8) END FROM ("S 1"."T 1" r1 INNER JOIN "S 1"."T 1" r2 ON (((r1."C 1" = r2."C 1")))) ORDER BY r1.c3 ASC NULLS LAST, r1."C 1" ASC NULLS LAST FOR SHARE OF r1 FOR SHARE OF r2
!                ->  Nested Loop
                       Output: t1.c1, t1.c3, t1.*, t2.c1, t2.*
!                      Join Filter: (t1.c1 = t2.c1)
!                      ->  Foreign Scan on public.ft1 t1
                             Output: t1.c1, t1.c3, t1.*
!                            Remote SQL: SELECT "C 1", c2, c3, c4, c5, c6, c7, c8 FROM "S 1"."T 1" FOR SHARE
!                      ->  Foreign Scan on public.ft2 t2
                             Output: t2.c1, t2.*
!                            Remote SQL: SELECT "C 1", c2, c3, c4, c5, c6, c7, c8 FROM "S 1"."T 1" FOR SHARE
! (17 rows)
  
  SELECT t1.c1, t2.c1 FROM ft1 t1 JOIN ft2 t2 ON (t1.c1 = t2.c1) ORDER BY t1.c3, t1.c1 OFFSET 100 LIMIT 10 FOR SHARE;
   c1  | c1  
***************
*** 1684,1689 **** SELECT t1.c1, t2.c1 FROM ft1 t1 JOIN ft2 t2 ON (t1.c1 = t2.c1) ORDER BY t1.c3, t
--- 1660,1726 ----
   110 | 110
  (10 rows)
  
+ -- FOR UPDATE/SHARE in situations where a full join is pushed down
+ EXPLAIN (VERBOSE, COSTS OFF)
+ SELECT t1.c1, t2.c1, t3.c1 FROM (SELECT c1 FROM "S 1"."T 3" WHERE c1 = 50) t1 INNER JOIN (ft4 t2 FULL JOIN ft5 t3 ON (t2.c1 = t3.c1)) ON (TRUE) ORDER BY t1.c1, t2.c1, t3.c1 FOR UPDATE OF t1;
+                                                                                                                                                      QUERY PLAN                                                                                                                                                      
+ ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
+  LockRows
+    Output: "T 3".c1, t2.c1, t3.c1, "T 3".ctid, t2.*, t3.*
+    ->  Nested Loop
+          Output: "T 3".c1, t2.c1, t3.c1, "T 3".ctid, t2.*, t3.*
+          ->  Foreign Scan
+                Output: t2.c1, t2.*, t3.c1, t3.*
+                Relations: (public.ft4 t2) FULL JOIN (public.ft5 t3)
+                Remote SQL: SELECT r2.c1, CASE WHEN (r2.*)::text IS NOT NULL THEN ROW(r2.c1, r2.c2, r2.c3) END, r3.c1, CASE WHEN (r3.*)::text IS NOT NULL THEN ROW(r3.c1, r3.c2, r3.c3) END FROM ("S 1"."T 3" r2 FULL JOIN "S 1"."T 4" r3 ON (((r2.c1 = r3.c1)))) ORDER BY r2.c1 ASC NULLS LAST, r3.c1 ASC NULLS LAST
+                ->  Hash Full Join
+                      Output: t2.c1, t2.*, t3.c1, t3.*
+                      Hash Cond: (t2.c1 = t3.c1)
+                      ->  Foreign Scan on public.ft4 t2
+                            Output: t2.c1, t2.*
+                            Remote SQL: SELECT c1, c2, c3 FROM "S 1"."T 3"
+                      ->  Hash
+                            Output: t3.c1, t3.*
+                            ->  Foreign Scan on public.ft5 t3
+                                  Output: t3.c1, t3.*
+                                  Remote SQL: SELECT c1, c2, c3 FROM "S 1"."T 4"
+          ->  Materialize
+                Output: "T 3".c1, "T 3".ctid
+                ->  Seq Scan on "S 1"."T 3"
+                      Output: "T 3".c1, "T 3".ctid
+                      Filter: ("T 3".c1 = 50)
+ (24 rows)
+ 
+ EXPLAIN (VERBOSE, COSTS OFF)
+ SELECT t1.c1, t2.c1, t3.c1 FROM (SELECT c1 FROM "S 1"."T 3" WHERE c1 = 50) t1 INNER JOIN (ft4 t2 FULL JOIN ft5 t3 ON (FALSE)) ON (TRUE) ORDER BY t1.c1, t2.c1, t3.c1 FOR UPDATE OF t1;
+                                                                                                                                                 QUERY PLAN                                                                                                                                                 
+ -----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
+  LockRows
+    Output: "T 3".c1, t2.c1, t3.c1, "T 3".ctid, t2.*, t3.*
+    ->  Nested Loop
+          Output: "T 3".c1, t2.c1, t3.c1, "T 3".ctid, t2.*, t3.*
+          ->  Foreign Scan
+                Output: t2.c1, t2.*, t3.c1, t3.*
+                Relations: (public.ft4 t2) FULL JOIN (public.ft5 t3)
+                Remote SQL: SELECT r2.c1, CASE WHEN (r2.*)::text IS NOT NULL THEN ROW(r2.c1, r2.c2, r2.c3) END, r3.c1, CASE WHEN (r3.*)::text IS NOT NULL THEN ROW(r3.c1, r3.c2, r3.c3) END FROM ("S 1"."T 3" r2 FULL JOIN "S 1"."T 4" r3 ON ((false))) ORDER BY r2.c1 ASC NULLS LAST, r3.c1 ASC NULLS LAST
+                ->  Merge Full Join
+                      Output: t2.c1, t2.*, t3.c1, t3.*
+                      Join Filter: false
+                      ->  Foreign Scan on public.ft4 t2
+                            Output: t2.c1, t2.*
+                            Remote SQL: SELECT c1, c2, c3 FROM "S 1"."T 3"
+                      ->  Materialize
+                            Output: t3.c1, t3.*
+                            ->  Foreign Scan on public.ft5 t3
+                                  Output: t3.c1, t3.*
+                                  Remote SQL: SELECT c1, c2, c3 FROM "S 1"."T 4"
+          ->  Materialize
+                Output: "T 3".c1, "T 3".ctid
+                ->  Seq Scan on "S 1"."T 3"
+                      Output: "T 3".c1, "T 3".ctid
+                      Filter: ("T 3".c1 = 50)
+ (24 rows)
+ 
  -- join in CTE
  EXPLAIN (VERBOSE, COSTS OFF)
  WITH t (c1_1, c1_3, c2_1) AS (SELECT t1.c1, t1.c3, t2.c1 FROM ft1 t1 JOIN ft2 t2 ON (t1.c1 = t2.c1)) SELECT c1_1, c2_1 FROM t ORDER BY c1_3, c1_1 OFFSET 100 LIMIT 10;
***************
*** 4016,4033 **** UPDATE ft2 SET c2 = ft2.c2 + 500, c3 = ft2.c3 || '_update9', c7 = DEFAULT
           Output: ft2.c1, (ft2.c2 + 500), NULL::integer, (ft2.c3 || '_update9'::text), ft2.c4, ft2.c5, ft2.c6, 'ft2       '::character(10), ft2.c8, ft2.ctid, ft1.*
           Relations: (public.ft2) INNER JOIN (public.ft1)
           Remote SQL: SELECT r1."C 1", r1.c2, r1.c3, r1.c4, r1.c5, r1.c6, r1.c8, r1.ctid, CASE WHEN (r2.*)::text IS NOT NULL THEN ROW(r2."C 1", r2.c2, r2.c3, r2.c4, r2.c5, r2.c6, r2.c7, r2.c8) END FROM ("S 1"."T 1" r1 INNER JOIN "S 1"."T 1" r2 ON (((r1.c2 = r2."C 1")) AND (((r2."C 1" % 10) = 9)))) FOR UPDATE OF r1
!          ->  Hash Join
                 Output: ft2.c1, ft2.c2, ft2.c3, ft2.c4, ft2.c5, ft2.c6, ft2.c8, ft2.ctid, ft1.*
!                Hash Cond: (ft2.c2 = ft1.c1)
                 ->  Foreign Scan on public.ft2
                       Output: ft2.c1, ft2.c2, ft2.c3, ft2.c4, ft2.c5, ft2.c6, ft2.c8, ft2.ctid
                       Remote SQL: SELECT "C 1", c2, c3, c4, c5, c6, c8, ctid FROM "S 1"."T 1" FOR UPDATE
!                ->  Hash
                       Output: ft1.*, ft1.c1
!                      ->  Foreign Scan on public.ft1
!                            Output: ft1.*, ft1.c1
!                            Remote SQL: SELECT "C 1", c2, c3, c4, c5, c6, c7, c8 FROM "S 1"."T 1" WHERE ((("C 1" % 10) = 9))
! (17 rows)
  
  UPDATE ft2 SET c2 = ft2.c2 + 500, c3 = ft2.c3 || '_update9', c7 = DEFAULT
    FROM ft1 WHERE ft1.c1 = ft2.c2 AND ft1.c1 % 10 = 9;
--- 4053,4068 ----
           Output: ft2.c1, (ft2.c2 + 500), NULL::integer, (ft2.c3 || '_update9'::text), ft2.c4, ft2.c5, ft2.c6, 'ft2       '::character(10), ft2.c8, ft2.ctid, ft1.*
           Relations: (public.ft2) INNER JOIN (public.ft1)
           Remote SQL: SELECT r1."C 1", r1.c2, r1.c3, r1.c4, r1.c5, r1.c6, r1.c8, r1.ctid, CASE WHEN (r2.*)::text IS NOT NULL THEN ROW(r2."C 1", r2.c2, r2.c3, r2.c4, r2.c5, r2.c6, r2.c7, r2.c8) END FROM ("S 1"."T 1" r1 INNER JOIN "S 1"."T 1" r2 ON (((r1.c2 = r2."C 1")) AND (((r2."C 1" % 10) = 9)))) FOR UPDATE OF r1
!          ->  Nested Loop
                 Output: ft2.c1, ft2.c2, ft2.c3, ft2.c4, ft2.c5, ft2.c6, ft2.c8, ft2.ctid, ft1.*
!                Join Filter: (ft2.c2 = ft1.c1)
                 ->  Foreign Scan on public.ft2
                       Output: ft2.c1, ft2.c2, ft2.c3, ft2.c4, ft2.c5, ft2.c6, ft2.c8, ft2.ctid
                       Remote SQL: SELECT "C 1", c2, c3, c4, c5, c6, c8, ctid FROM "S 1"."T 1" FOR UPDATE
!                ->  Foreign Scan on public.ft1
                       Output: ft1.*, ft1.c1
!                      Remote SQL: SELECT "C 1", c2, c3, c4, c5, c6, c7, c8 FROM "S 1"."T 1" WHERE ((("C 1" % 10) = 9))
! (15 rows)
  
  UPDATE ft2 SET c2 = ft2.c2 + 500, c3 = ft2.c3 || '_update9', c7 = DEFAULT
    FROM ft1 WHERE ft1.c1 = ft2.c2 AND ft1.c1 % 10 = 9;
***************
*** 4159,4176 **** DELETE FROM ft2 USING ft1 WHERE ft1.c1 = ft2.c2 AND ft1.c1 % 10 = 2;
           Output: ft2.ctid, ft1.*
           Relations: (public.ft2) INNER JOIN (public.ft1)
           Remote SQL: SELECT r1.ctid, CASE WHEN (r2.*)::text IS NOT NULL THEN ROW(r2."C 1", r2.c2, r2.c3, r2.c4, r2.c5, r2.c6, r2.c7, r2.c8) END FROM ("S 1"."T 1" r1 INNER JOIN "S 1"."T 1" r2 ON (((r1.c2 = r2."C 1")) AND (((r2."C 1" % 10) = 2)))) FOR UPDATE OF r1
!          ->  Hash Join
                 Output: ft2.ctid, ft1.*
!                Hash Cond: (ft2.c2 = ft1.c1)
                 ->  Foreign Scan on public.ft2
                       Output: ft2.ctid, ft2.c2
                       Remote SQL: SELECT c2, ctid FROM "S 1"."T 1" FOR UPDATE
!                ->  Hash
                       Output: ft1.*, ft1.c1
!                      ->  Foreign Scan on public.ft1
!                            Output: ft1.*, ft1.c1
!                            Remote SQL: SELECT "C 1", c2, c3, c4, c5, c6, c7, c8 FROM "S 1"."T 1" WHERE ((("C 1" % 10) = 2))
! (17 rows)
  
  DELETE FROM ft2 USING ft1 WHERE ft1.c1 = ft2.c2 AND ft1.c1 % 10 = 2;
  SELECT c1,c2,c3,c4 FROM ft2 ORDER BY c1;
--- 4194,4209 ----
           Output: ft2.ctid, ft1.*
           Relations: (public.ft2) INNER JOIN (public.ft1)
           Remote SQL: SELECT r1.ctid, CASE WHEN (r2.*)::text IS NOT NULL THEN ROW(r2."C 1", r2.c2, r2.c3, r2.c4, r2.c5, r2.c6, r2.c7, r2.c8) END FROM ("S 1"."T 1" r1 INNER JOIN "S 1"."T 1" r2 ON (((r1.c2 = r2."C 1")) AND (((r2."C 1" % 10) = 2)))) FOR UPDATE OF r1
!          ->  Nested Loop
                 Output: ft2.ctid, ft1.*
!                Join Filter: (ft2.c2 = ft1.c1)
                 ->  Foreign Scan on public.ft2
                       Output: ft2.ctid, ft2.c2
                       Remote SQL: SELECT c2, ctid FROM "S 1"."T 1" FOR UPDATE
!                ->  Foreign Scan on public.ft1
                       Output: ft1.*, ft1.c1
!                      Remote SQL: SELECT "C 1", c2, c3, c4, c5, c6, c7, c8 FROM "S 1"."T 1" WHERE ((("C 1" % 10) = 2))
! (15 rows)
  
  DELETE FROM ft2 USING ft1 WHERE ft1.c1 = ft2.c2 AND ft1.c1 % 10 = 2;
  SELECT c1,c2,c3,c4 FROM ft2 ORDER BY c1;
*** a/contrib/postgres_fdw/postgres_fdw.c
--- b/contrib/postgres_fdw/postgres_fdw.c
***************
*** 4365,4374 **** postgresGetForeignJoinPaths(PlannerInfo *root,
  		root->parse->commandType == CMD_UPDATE ||
  		root->rowMarks)
  	{
! 		epq_path = GetExistingLocalJoinPath(joinrel);
  		if (!epq_path)
  		{
! 			elog(DEBUG3, "could not push down foreign join because a local path suitable for EPQ checks was not found");
  			return;
  		}
  	}
--- 4365,4375 ----
  		root->parse->commandType == CMD_UPDATE ||
  		root->rowMarks)
  	{
! 		epq_path = CreateLocalJoinPath(root, joinrel, outerrel, innerrel,
! 									   jointype, extra);
  		if (!epq_path)
  		{
! 			elog(DEBUG3, "could not push down foreign join because a local path suitable for EPQ checks was not created");
  			return;
  		}
  	}
*** a/contrib/postgres_fdw/sql/postgres_fdw.sql
--- b/contrib/postgres_fdw/sql/postgres_fdw.sql
***************
*** 445,450 **** SELECT t1.c1, t2.c1 FROM ft1 t1 JOIN ft2 t2 ON (t1.c1 = t2.c1) ORDER BY t1.c3, t
--- 445,455 ----
  EXPLAIN (VERBOSE, COSTS OFF)
  SELECT t1.c1, t2.c1 FROM ft1 t1 JOIN ft2 t2 ON (t1.c1 = t2.c1) ORDER BY t1.c3, t1.c1 OFFSET 100 LIMIT 10 FOR SHARE;
  SELECT t1.c1, t2.c1 FROM ft1 t1 JOIN ft2 t2 ON (t1.c1 = t2.c1) ORDER BY t1.c3, t1.c1 OFFSET 100 LIMIT 10 FOR SHARE;
+ -- FOR UPDATE/SHARE in situations where a full join is pushed down
+ EXPLAIN (VERBOSE, COSTS OFF)
+ SELECT t1.c1, t2.c1, t3.c1 FROM (SELECT c1 FROM "S 1"."T 3" WHERE c1 = 50) t1 INNER JOIN (ft4 t2 FULL JOIN ft5 t3 ON (t2.c1 = t3.c1)) ON (TRUE) ORDER BY t1.c1, t2.c1, t3.c1 FOR UPDATE OF t1;
+ EXPLAIN (VERBOSE, COSTS OFF)
+ SELECT t1.c1, t2.c1, t3.c1 FROM (SELECT c1 FROM "S 1"."T 3" WHERE c1 = 50) t1 INNER JOIN (ft4 t2 FULL JOIN ft5 t3 ON (FALSE)) ON (TRUE) ORDER BY t1.c1, t2.c1, t3.c1 FOR UPDATE OF t1;
  -- join in CTE
  EXPLAIN (VERBOSE, COSTS OFF)
  WITH t (c1_1, c1_3, c2_1) AS (SELECT t1.c1, t1.c3, t2.c1 FROM ft1 t1 JOIN ft2 t2 ON (t1.c1 = t2.c1)) SELECT c1_1, c2_1 FROM t ORDER BY c1_3, c1_1 OFFSET 100 LIMIT 10;
*** a/doc/src/sgml/fdwhandler.sgml
--- b/doc/src/sgml/fdwhandler.sgml
***************
*** 995,1007 **** RecheckForeignScan (ForeignScanState *node, TupleTableSlot *slot);
       can be executed and the resulting tuple can be stored in the slot.
       This plan need not be efficient since no base table will return more
       than one row; for example, it may implement all joins as nested loops.
!      The function <literal>GetExistingLocalJoinPath</> may be used to search
!      existing paths for a suitable local join path, which can be used as the
!      alternative local join plan.  <literal>GetExistingLocalJoinPath</>
!      searches for an unparameterized path in the path list of the specified
!      join relation.  (If it does not find such a path, it returns NULL, in
!      which case a foreign data wrapper may build the local path by itself or
!      may choose not to create access paths for that join.)
      </para>
     </sect2>
  
--- 995,1008 ----
       can be executed and the resulting tuple can be stored in the slot.
       This plan need not be efficient since no base table will return more
       than one row; for example, it may implement all joins as nested loops.
!      The function <literal>CreateLocalJoinPath</> may be used to build
!      a suitable local join path, which can be used as the alternative local
!      join plan.  <literal>CreateLocalJoinPath</> builds a nested loop join
!      path for the specified join relation, except when the join type is
!      <literal>FULL</>, in which case a merge or hash join path is built.
!      (If it does not build such a path, it returns NULL, in which case a
!      foreign data wrapper may build the local path by itself or may choose
!      not to create access paths for that join.)
      </para>
     </sect2>
  
*** a/src/backend/foreign/foreign.c
--- b/src/backend/foreign/foreign.c
***************
*** 22,27 ****
--- 22,29 ----
  #include "foreign/foreign.h"
  #include "lib/stringinfo.h"
  #include "miscadmin.h"
+ #include "optimizer/cost.h"
+ #include "optimizer/pathnode.h"
  #include "utils/builtins.h"
  #include "utils/memutils.h"
  #include "utils/rel.h"
***************
*** 693,805 **** get_foreign_server_oid(const char *servername, bool missing_ok)
  	return oid;
  }
  
  /*
!  * Get a copy of an existing local path for a given join relation.
!  *
!  * This function is usually helpful to obtain an alternate local path for EPQ
!  * checks.
!  *
!  * Right now, this function only supports unparameterized foreign joins, so we
!  * only search for unparameterized path in the given list of paths. Since we
!  * are searching for a path which can be used to construct an alternative local
!  * plan for a foreign join, we look for only MergeJoin, HashJoin or NestLoop
!  * paths.
!  *
!  * If the inner or outer subpath of the chosen path is a ForeignScan, we
!  * replace it with its outer subpath.  For this reason, and also because the
!  * planner might free the original path later, the path returned by this
!  * function is a shallow copy of the original.  There's no need to copy
!  * the substructure, so we don't.
   *
!  * Since the plan created using this path will presumably only be used to
!  * execute EPQ checks, efficiency of the path is not a concern. But since the
!  * path list in RelOptInfo is anyway sorted by total cost we are likely to
!  * choose the most efficient path, which is all for the best.
   */
! extern Path *
! GetExistingLocalJoinPath(RelOptInfo *joinrel)
  {
! 	ListCell   *lc;
! 
! 	Assert(joinrel->reloptkind == RELOPT_JOINREL);
  
! 	foreach(lc, joinrel->pathlist)
  	{
! 		Path	   *path = (Path *) lfirst(lc);
! 		JoinPath   *joinpath = NULL;
! 
! 		/* Skip parameterised paths. */
! 		if (path->param_info != NULL)
! 			continue;
! 
! 		switch (path->pathtype)
! 		{
! 			case T_HashJoin:
! 				{
! 					HashPath   *hash_path = makeNode(HashPath);
! 
! 					memcpy(hash_path, path, sizeof(HashPath));
! 					joinpath = (JoinPath *) hash_path;
! 				}
! 				break;
! 
! 			case T_NestLoop:
  				{
! 					NestPath   *nest_path = makeNode(NestPath);
! 
! 					memcpy(nest_path, path, sizeof(NestPath));
! 					joinpath = (JoinPath *) nest_path;
  				}
! 				break;
! 
! 			case T_MergeJoin:
  				{
! 					MergePath  *merge_path = makeNode(MergePath);
  
! 					memcpy(merge_path, path, sizeof(MergePath));
! 					joinpath = (JoinPath *) merge_path;
  				}
! 				break;
! 
! 			default:
! 
! 				/*
! 				 * Just skip anything else. We don't know if corresponding
! 				 * plan would build the output row from whole-row references
! 				 * of base relations and execute the EPQ checks.
! 				 */
! 				break;
! 		}
! 
! 		/* This path isn't good for us, check next. */
! 		if (!joinpath)
! 			continue;
! 
! 		/*
! 		 * 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;
! 		}
! 
! 		if (IsA(joinpath->innerjoinpath, ForeignPath))
! 		{
! 			ForeignPath *foreign_path;
! 
! 			foreign_path = (ForeignPath *) joinpath->innerjoinpath;
! 			if (foreign_path->path.parent->reloptkind == RELOPT_JOINREL)
! 				joinpath->innerjoinpath = foreign_path->fdw_outerpath;
! 		}
! 
! 		return (Path *) joinpath;
  	}
! 	return NULL;
  }
--- 695,880 ----
  	return oid;
  }
  
+ 
  /*
!  * Make a local join path for a foreign join
   *
!  * Note: currently, this function only supports unparameterized foreign joins.
   */
! Path *
! CreateLocalJoinPath(PlannerInfo *root,
! 					RelOptInfo *joinrel,
! 					RelOptInfo *outerrel,
! 					RelOptInfo *innerrel,
! 					JoinType jointype,
! 					JoinPathExtraData *extra)
  {
! 	Path	   *outer_path = outerrel->cheapest_total_path;
! 	Path	   *inner_path = innerrel->cheapest_total_path;
! 	Path	   *result;
! 	Relids		required_outer;
! 	JoinCostWorkspace workspace;
  
! 	/*
! 	 * Generate a nestloop path (or hashjoin/mergejoin path, if full join)
! 	 * from the cheapest-total paths for the outer and inner relations.  (The
! 	 * point here is to avoid using a mergejoin, if possible, because that
! 	 * has assumptions about input ordering that likely won't be satisfied by
! 	 * the cheapest-total paths for the outer and inner relations.)
! 	 */
! 	switch (jointype)
  	{
! 		case JOIN_INNER:
! 		case JOIN_LEFT:
! 		case JOIN_SEMI:
! 		case JOIN_ANTI:
! 			/*
! 			 * If the outer cheapest-total path is parameterized by the inner
! 			 * rel, we can't generate a nestloop path.  (There's no use
! 			 * looking for alternative outer paths, since it should already be
! 			 * the least-parameterized available path.)
! 			 */
! 			if (PATH_PARAM_BY_REL(outer_path, innerrel))
! 				return NULL;
! 			/* If proposed path is still parameterized, we can't use it. */
! 			required_outer = calc_nestloop_required_outer(outer_path,
! 														  inner_path);
! 			if (required_outer)
! 			{
! 				bms_free(required_outer);
! 				return NULL;
! 			}
! 			/* Get initial estimates */
! 			initial_cost_nestloop(root, &workspace, jointype,
! 								  outer_path, inner_path,
! 								  extra->sjinfo, &extra->semifactors);
! 			/* Generate a nestloop path */
! 			result = (Path *) create_nestloop_path(root,
! 												   joinrel,
! 												   jointype,
! 												   &workspace,
! 												   extra->sjinfo,
! 												   &extra->semifactors,
! 												   outer_path,
! 												   inner_path,
! 												   extra->restrictlist,
! 												   NIL, NULL);
! 			break;
! 		case JOIN_FULL:
! 			/*
! 			 * If either cheapest-total path is parameterized by the other
! 			 * rel, we can't generate a hashjoin/mergejoin path.  (There's no
! 			 * use looking for alternative input paths, since these should
! 			 * already be the least-parameterized available paths.)
! 			 */
! 			if (PATH_PARAM_BY_REL(outer_path, innerrel) ||
! 				PATH_PARAM_BY_REL(inner_path, outerrel))
! 				return NULL;
! 			/* If proposed path is still parameterized, we can't use it. */
! 			required_outer = calc_non_nestloop_required_outer(outer_path,
! 															  inner_path);
! 			if (required_outer)
! 			{
! 				bms_free(required_outer);
! 				return NULL;
! 			}
! 			/*
! 			 * Create a hashjoin path, if possible.  Else create a mergejoin
! 			 * path, if possible.
! 			 */
! 			if (extra->hashclause_list)
! 			{
! 				/* Get initial estimates */
! 				initial_cost_hashjoin(root, &workspace, jointype,
! 									  extra->hashclause_list,
! 									  outer_path, inner_path,
! 									  extra->sjinfo, &extra->semifactors);
! 				/* Generate a hashjoin path */
! 				result = (Path *) create_hashjoin_path(root,
! 													   joinrel,
! 													   jointype,
! 													   &workspace,
! 													   extra->sjinfo,
! 													   &extra->semifactors,
! 													   outer_path,
! 													   inner_path,
! 													   extra->restrictlist,
! 													   NULL,
! 													   extra->hashclause_list);
! 			}
! 			else if (extra->mergejoin_allowed)
! 			{
! 				/*
! 				 * If special case: for "x FULL JOIN y ON true", there will be
! 				 * no join clauses at all; create a clauseless mergejoin path.
! 				 * Else create a mergejoin path by explicitly sorting both the
! 				 * outer and inner relations as in sort_inner_and_outer.
! 				 */
! 				if (!extra->mergeclause_list)
  				{
! 					/* Get initial estimates */
! 					initial_cost_mergejoin(root, &workspace, jointype, NIL,
! 										   outer_path, inner_path, NIL, NIL,
! 										   extra->sjinfo);
! 					/* Generate a mergejoin path */
! 					result = (Path *) create_mergejoin_path(root,
! 															joinrel,
! 															jointype,
! 															&workspace,
! 															extra->sjinfo,
! 															outer_path,
! 															inner_path,
! 															extra->restrictlist,
! 															NIL, NULL,
! 															NIL, NIL, NIL);
  				}
! 				else
  				{
! 					List	   *outerkeys = extra->merge_outerkeys;
! 					List	   *innerkeys = extra->merge_innerkeys;
  
! 					/*
! 					 * If the paths are already well enough ordered, we can
! 					 * skip doing an explicit sort.
! 					 */
! 					if (outerkeys &&
! 						pathkeys_contained_in(outerkeys, outer_path->pathkeys))
! 						outerkeys = NIL;
! 					if (innerkeys &&
! 						pathkeys_contained_in(innerkeys, inner_path->pathkeys))
! 						innerkeys = NIL;
! 					/* Get initial estimates */
! 					initial_cost_mergejoin(root, &workspace, jointype,
! 										   extra->mergeclauses,
! 										   outer_path, inner_path,
! 										   outerkeys, innerkeys,
! 										   extra->sjinfo);
! 					/* Generate a mergejoin path */
! 					result = (Path *) create_mergejoin_path(root,
! 															joinrel,
! 															jointype,
! 															&workspace,
! 															extra->sjinfo,
! 															outer_path,
! 															inner_path,
! 															extra->restrictlist,
! 															extra->merge_pathkeys,
! 															NULL,
! 															extra->mergeclauses,
! 															outerkeys,
! 															innerkeys);
  				}
! 			}
! 			else
! 				result = NULL;
! 			break;
! 		default:
! 			/* other values not expected here */
! 			elog(ERROR, "unrecognized join type: %d",
! 				 (int) jointype);
! 			result = NULL; /* keep compiler quiet */
! 			break;
  	}
! 
! 	return result;
  }
*** a/src/backend/optimizer/path/joinpath.c
--- b/src/backend/optimizer/path/joinpath.c
***************
*** 25,33 ****
  /* Hook for plugins to get control in add_paths_to_joinrel() */
  set_join_pathlist_hook_type set_join_pathlist_hook = NULL;
  
- #define PATH_PARAM_BY_REL(path, rel)  \
- 	((path)->param_info && bms_overlap(PATH_REQ_OUTER(path), (rel)->relids))
- 
  static void sort_inner_and_outer(PlannerInfo *root, RelOptInfo *joinrel,
  					 RelOptInfo *outerrel, RelOptInfo *innerrel,
  					 JoinType jointype, JoinPathExtraData *extra);
--- 25,30 ----
***************
*** 85,97 **** add_paths_to_joinrel(PlannerInfo *root,
  					 List *restrictlist)
  {
  	JoinPathExtraData extra;
- 	bool		mergejoin_allowed = true;
  	ListCell   *lc;
  
  	extra.restrictlist = restrictlist;
  	extra.mergeclause_list = NIL;
  	extra.sjinfo = sjinfo;
  	extra.param_source_rels = NULL;
  
  	/*
  	 * Find potential mergejoin clauses.  We can skip this if we are not
--- 82,99 ----
  					 List *restrictlist)
  {
  	JoinPathExtraData extra;
  	ListCell   *lc;
  
  	extra.restrictlist = restrictlist;
  	extra.mergeclause_list = NIL;
+ 	extra.hashclause_list = NIL;
+ 	extra.mergejoin_allowed = true;
  	extra.sjinfo = sjinfo;
  	extra.param_source_rels = NULL;
+ 	extra.mergeclauses = NIL;
+ 	extra.merge_pathkeys = NIL;
+ 	extra.merge_outerkeys = NIL;
+ 	extra.merge_innerkeys = NIL;
  
  	/*
  	 * Find potential mergejoin clauses.  We can skip this if we are not
***************
*** 106,112 **** add_paths_to_joinrel(PlannerInfo *root,
  														  innerrel,
  														  restrictlist,
  														  jointype,
! 														  &mergejoin_allowed);
  
  	/*
  	 * If it's SEMI or ANTI join, compute correction factors for cost
--- 108,114 ----
  														  innerrel,
  														  restrictlist,
  														  jointype,
! 													&extra.mergejoin_allowed);
  
  	/*
  	 * If it's SEMI or ANTI join, compute correction factors for cost
***************
*** 169,175 **** add_paths_to_joinrel(PlannerInfo *root,
  	 * 1. Consider mergejoin paths where both relations must be explicitly
  	 * sorted.  Skip this if we can't mergejoin.
  	 */
! 	if (mergejoin_allowed)
  		sort_inner_and_outer(root, joinrel, outerrel, innerrel,
  							 jointype, &extra);
  
--- 171,177 ----
  	 * 1. Consider mergejoin paths where both relations must be explicitly
  	 * sorted.  Skip this if we can't mergejoin.
  	 */
! 	if (extra.mergejoin_allowed)
  		sort_inner_and_outer(root, joinrel, outerrel, innerrel,
  							 jointype, &extra);
  
***************
*** 180,186 **** add_paths_to_joinrel(PlannerInfo *root,
  	 * (That's okay because we know that nestloop can't handle right/full
  	 * joins at all, so it wouldn't work in the prohibited cases either.)
  	 */
! 	if (mergejoin_allowed)
  		match_unsorted_outer(root, joinrel, outerrel, innerrel,
  							 jointype, &extra);
  
--- 182,188 ----
  	 * (That's okay because we know that nestloop can't handle right/full
  	 * joins at all, so it wouldn't work in the prohibited cases either.)
  	 */
! 	if (extra.mergejoin_allowed)
  		match_unsorted_outer(root, joinrel, outerrel, innerrel,
  							 jointype, &extra);
  
***************
*** 197,203 **** add_paths_to_joinrel(PlannerInfo *root,
  	 * those made by match_unsorted_outer when add_paths_to_joinrel() is
  	 * invoked with the two rels given in the other order.
  	 */
! 	if (mergejoin_allowed)
  		match_unsorted_inner(root, joinrel, outerrel, innerrel,
  							 jointype, &extra);
  #endif
--- 199,205 ----
  	 * those made by match_unsorted_outer when add_paths_to_joinrel() is
  	 * invoked with the two rels given in the other order.
  	 */
! 	if (extra.mergejoin_allowed)
  		match_unsorted_inner(root, joinrel, outerrel, innerrel,
  							 jointype, &extra);
  #endif
***************
*** 773,778 **** sort_inner_and_outer(PlannerInfo *root,
--- 775,789 ----
  						   innerkeys,
  						   jointype,
  						   extra);
+ 
+ 		/* Save first mergejoin information for possible use by the FDW */
+ 		if (outerkeys == all_pathkeys)
+ 		{
+ 			extra->mergeclauses = cur_mergeclauses;
+ 			extra->merge_pathkeys = merge_pathkeys;
+ 			extra->merge_outerkeys = outerkeys;
+ 			extra->merge_innerkeys = innerkeys;
+ 		}
  	}
  }
  
***************
*** 1320,1325 **** hash_inner_and_outer(PlannerInfo *root,
--- 1331,1339 ----
  		hashclauses = lappend(hashclauses, restrictinfo);
  	}
  
+ 	/* Save hashclauses for possible use by the FDW */
+ 	extra->hashclause_list = hashclauses;
+ 
  	/* If we found any usable hashclauses, make paths */
  	if (hashclauses)
  	{
*** a/src/include/foreign/fdwapi.h
--- b/src/include/foreign/fdwapi.h
***************
*** 235,240 **** extern FdwRoutine *GetFdwRoutineByRelId(Oid relid);
  extern FdwRoutine *GetFdwRoutineForRelation(Relation relation, bool makecopy);
  extern bool IsImportableForeignTable(const char *tablename,
  						 ImportForeignSchemaStmt *stmt);
! extern Path *GetExistingLocalJoinPath(RelOptInfo *joinrel);
  
  #endif   /* FDWAPI_H */
--- 235,242 ----
  extern FdwRoutine *GetFdwRoutineForRelation(Relation relation, bool makecopy);
  extern bool IsImportableForeignTable(const char *tablename,
  						 ImportForeignSchemaStmt *stmt);
! extern Path *CreateLocalJoinPath(PlannerInfo *root, RelOptInfo *joinrel,
! 					RelOptInfo *outerrel, RelOptInfo *innerrel,
! 					JoinType jointype, JoinPathExtraData *extra);
  
  #endif   /* FDWAPI_H */
*** a/src/include/nodes/relation.h
--- b/src/include/nodes/relation.h
***************
*** 904,909 **** typedef struct Path
--- 904,913 ----
  #define PATH_REQ_OUTER(path)  \
  	((path)->param_info ? (path)->param_info->ppi_req_outer : (Relids) NULL)
  
+ /* Macro for determining whether path is parameterized by rel */
+ #define PATH_PARAM_BY_REL(path, rel)  \
+ 	((path)->param_info && bms_overlap(PATH_REQ_OUTER(path), (rel)->relids))
+ 
  /*----------
   * IndexPath represents an index scan over a single index.
   *
***************
*** 2006,2022 **** typedef struct SemiAntiJoinFactors
--- 2010,2040 ----
   *		clauses that apply to this join
   * mergeclause_list is a list of RestrictInfo nodes for available
   *		mergejoin clauses in this join
+  * hashclause_list is a list of RestrictInfo nodes for available
+  *		hashjoin clauses in this join
+  * mergejoin_allowed is a flag to indicate whether mergejoins are allowed
   * sjinfo is extra info about special joins for selectivity estimation
   * semifactors is as shown above (only valid for SEMI or ANTI joins)
   * param_source_rels are OK targets for parameterization of result paths
+  * mergeclauses are the RestrictInfo nodes to be used as merge clauses for
+  *		a mergejoin path
+  * merge_pathkeys are the pathkeys of the mergejoin path
+  * merge_outerkeys are the sort pathkeys for the outer relation
+  * merge_innerkeys are the sort pathkeys for the inner relation
   */
  typedef struct JoinPathExtraData
  {
  	List	   *restrictlist;
  	List	   *mergeclause_list;
+ 	List	   *hashclause_list;
+ 	bool		mergejoin_allowed;
  	SpecialJoinInfo *sjinfo;
  	SemiAntiJoinFactors semifactors;
  	Relids		param_source_rels;
+ 	List	   *mergeclauses;
+ 	List	   *merge_pathkeys;
+ 	List	   *merge_outerkeys;
+ 	List	   *merge_innerkeys;
  } JoinPathExtraData;
  
  /*
-- 
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