postgres_fdw: Avoid 'variable not found in subplan target list' error.

The tlist of the EvalPlanQual outer plan for a ForeignScan node is
adjusted to produce a tuple whose descriptor matches the scan tuple slot
for the ForeignScan node.  But in the case where the outer plan contains
an extra Sort node, if the new tlist contained columns required only for
evaluating PlaceHolderVars or columns required only for evaluating local
conditions, this would cause setrefs.c to fail with the error.

The cause of this is that when creating the outer plan by injecting the
Sort node into an alternative local join plan that could emit such extra
columns as well, we fail to arrange for the outer plan to propagate them
up through the Sort node, causing setrefs.c to fail to match up them in
the new tlist to what is available from the outer plan.  Repair.

Per report from Alexander Pyhalov.

Richard Guo and Etsuro Fujita, reviewed by Alexander Pyhalov and Tom Lane.
Backpatch to all supported versions.

Discussion: http://postgr.es/m/cfb17bf6dfdf876467bd5ef533852d18%40postgrespro.ru

Author: Etsuro Fujita

contrib/postgres_fdw/expected/postgres_fdw.out

@@ -2474,6 +2474,85 @@ SELECT * FROM ft1, ft2, ft4, ft5, local_tbl WHERE ft1.c1 = ft2.c1 AND ft1.c2 = f
 
 RESET enable_nestloop;
 RESET enable_hashjoin;
+-- test that add_paths_with_pathkeys_for_rel() arranges for the epq_path to
+-- return columns needed by the parent ForeignScan node
+EXPLAIN (VERBOSE, COSTS OFF)
+SELECT * FROM local_tbl LEFT JOIN (SELECT ft1.*, COALESCE(ft1.c3 || ft2.c3, 'foobar') FROM ft1 INNER JOIN ft2 ON (ft1.c1 = ft2.c1 AND ft1.c1 < 100)) ss ON (local_tbl.c1 = ss.c1) ORDER BY local_tbl.c1 FOR UPDATE OF local_tbl;
+                                                                                                                                                                                                                              QUERY PLAN                                                                                                                                                                                                                              
+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
+ LockRows
+   Output: local_tbl.c1, local_tbl.c2, local_tbl.c3, ft1.c1, ft1.c2, ft1.c3, ft1.c4, ft1.c5, ft1.c6, ft1.c7, ft1.c8, (COALESCE((ft1.c3 || ft2.c3), 'foobar'::text)), local_tbl.ctid, ft1.*, ft2.*
+   ->  Merge Left Join
+         Output: local_tbl.c1, local_tbl.c2, local_tbl.c3, ft1.c1, ft1.c2, ft1.c3, ft1.c4, ft1.c5, ft1.c6, ft1.c7, ft1.c8, (COALESCE((ft1.c3 || ft2.c3), 'foobar'::text)), local_tbl.ctid, ft1.*, ft2.*
+         Merge Cond: (local_tbl.c1 = ft1.c1)
+         ->  Index Scan using local_tbl_pkey on public.local_tbl
+               Output: local_tbl.c1, local_tbl.c2, local_tbl.c3, local_tbl.ctid
+         ->  Materialize
+               Output: ft1.c1, ft1.c2, ft1.c3, ft1.c4, ft1.c5, ft1.c6, ft1.c7, ft1.c8, ft1.*, ft2.*, (COALESCE((ft1.c3 || ft2.c3), 'foobar'::text))
+               ->  Foreign Scan
+                     Output: ft1.c1, ft1.c2, ft1.c3, ft1.c4, ft1.c5, ft1.c6, ft1.c7, ft1.c8, ft1.*, ft2.*, COALESCE((ft1.c3 || ft2.c3), 'foobar'::text)
+                     Relations: (public.ft1) INNER JOIN (public.ft2)
+                     Remote SQL: SELECT r4."C 1", r4.c2, r4.c3, r4.c4, r4.c5, r4.c6, r4.c7, r4.c8, CASE WHEN (r4.*)::text IS NOT NULL THEN ROW(r4."C 1", r4.c2, r4.c3, r4.c4, r4.c5, r4.c6, r4.c7, r4.c8) END, CASE WHEN (r5.*)::text IS NOT NULL THEN ROW(r5."C 1", r5.c2, r5.c3, r5.c4, r5.c5, r5.c6, r5.c7, r5.c8) END, r5.c3 FROM ("S 1"."T 1" r4 INNER JOIN "S 1"."T 1" r5 ON (((r4."C 1" = r5."C 1")) AND ((r4."C 1" < 100)))) ORDER BY r4."C 1" ASC NULLS LAST
+                     ->  Result
+                           Output: ft1.c1, ft1.c2, ft1.c3, ft1.c4, ft1.c5, ft1.c6, ft1.c7, ft1.c8, ft1.*, ft2.*, ft2.c3
+                           ->  Sort
+                                 Output: ft1.c1, ft1.c2, ft1.c3, ft1.c4, ft1.c5, ft1.c6, ft1.c7, ft1.c8, ft1.*, ft2.*, (COALESCE((ft1.c3 || ft2.c3), 'foobar'::text)), ft2.c3
+                                 Sort Key: ft1.c1
+                                 ->  Hash Join
+                                       Output: ft1.c1, ft1.c2, ft1.c3, ft1.c4, ft1.c5, ft1.c6, ft1.c7, ft1.c8, ft1.*, ft2.*, COALESCE((ft1.c3 || ft2.c3), 'foobar'::text), ft2.c3
+                                       Hash Cond: (ft1.c1 = ft2.c1)
+                                       ->  Foreign Scan on public.ft1
+                                             Output: ft1.c1, ft1.c2, ft1.c3, ft1.c4, ft1.c5, ft1.c6, ft1.c7, ft1.c8, ft1.*
+                                             Remote SQL: SELECT "C 1", c2, c3, c4, c5, c6, c7, c8 FROM "S 1"."T 1" WHERE (("C 1" < 100))
+                                       ->  Hash
+                                             Output: ft2.*, ft2.c1, ft2.c3
+                                             ->  Foreign Scan on public.ft2
+                                                   Output: ft2.*, ft2.c1, ft2.c3
+                                                   Remote SQL: SELECT "C 1", c2, c3, c4, c5, c6, c7, c8 FROM "S 1"."T 1"
+(29 rows)
+
+ALTER SERVER loopback OPTIONS (DROP extensions);
+ALTER SERVER loopback OPTIONS (ADD fdw_startup_cost '10000.0');
+EXPLAIN (VERBOSE, COSTS OFF)
+SELECT * FROM local_tbl LEFT JOIN (SELECT ft1.* FROM ft1 INNER JOIN ft2 ON (ft1.c1 = ft2.c1 AND ft1.c1 < 100 AND ft1.c1 = postgres_fdw_abs(ft2.c2))) ss ON (local_tbl.c3 = ss.c3) ORDER BY local_tbl.c1 FOR UPDATE OF local_tbl;
+                                                                                                                                                                                                                            QUERY PLAN                                                                                                                                                                                                                             
+-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
+ LockRows
+   Output: local_tbl.c1, local_tbl.c2, local_tbl.c3, ft1.c1, ft1.c2, ft1.c3, ft1.c4, ft1.c5, ft1.c6, ft1.c7, ft1.c8, local_tbl.ctid, ft1.*, ft2.*
+   ->  Nested Loop Left Join
+         Output: local_tbl.c1, local_tbl.c2, local_tbl.c3, ft1.c1, ft1.c2, ft1.c3, ft1.c4, ft1.c5, ft1.c6, ft1.c7, ft1.c8, local_tbl.ctid, ft1.*, ft2.*
+         Join Filter: (local_tbl.c3 = ft1.c3)
+         ->  Index Scan using local_tbl_pkey on public.local_tbl
+               Output: local_tbl.c1, local_tbl.c2, local_tbl.c3, local_tbl.ctid
+         ->  Materialize
+               Output: ft1.c1, ft1.c2, ft1.c3, ft1.c4, ft1.c5, ft1.c6, ft1.c7, ft1.c8, ft1.*, ft2.*
+               ->  Foreign Scan
+                     Output: ft1.c1, ft1.c2, ft1.c3, ft1.c4, ft1.c5, ft1.c6, ft1.c7, ft1.c8, ft1.*, ft2.*
+                     Filter: (ft1.c1 = postgres_fdw_abs(ft2.c2))
+                     Relations: (public.ft1) INNER JOIN (public.ft2)
+                     Remote SQL: SELECT r4."C 1", r4.c2, r4.c3, r4.c4, r4.c5, r4.c6, r4.c7, r4.c8, CASE WHEN (r4.*)::text IS NOT NULL THEN ROW(r4."C 1", r4.c2, r4.c3, r4.c4, r4.c5, r4.c6, r4.c7, r4.c8) END, CASE WHEN (r5.*)::text IS NOT NULL THEN ROW(r5."C 1", r5.c2, r5.c3, r5.c4, r5.c5, r5.c6, r5.c7, r5.c8) END, r5.c2 FROM ("S 1"."T 1" r4 INNER JOIN "S 1"."T 1" r5 ON (((r4."C 1" = r5."C 1")) AND ((r4."C 1" < 100)))) ORDER BY r4.c3 ASC NULLS LAST
+                     ->  Sort
+                           Output: ft1.c1, ft1.c2, ft1.c3, ft1.c4, ft1.c5, ft1.c6, ft1.c7, ft1.c8, ft1.*, ft2.*, ft2.c2
+                           Sort Key: ft1.c3
+                           ->  Merge Join
+                                 Output: ft1.c1, ft1.c2, ft1.c3, ft1.c4, ft1.c5, ft1.c6, ft1.c7, ft1.c8, ft1.*, ft2.*, ft2.c2
+                                 Merge Cond: ((ft1.c1 = (postgres_fdw_abs(ft2.c2))) AND (ft1.c1 = ft2.c1))
+                                 ->  Sort
+                                       Output: ft1.c1, ft1.c2, ft1.c3, ft1.c4, ft1.c5, ft1.c6, ft1.c7, ft1.c8, ft1.*
+                                       Sort Key: ft1.c1
+                                       ->  Foreign Scan on public.ft1
+                                             Output: ft1.c1, ft1.c2, ft1.c3, ft1.c4, ft1.c5, ft1.c6, ft1.c7, ft1.c8, ft1.*
+                                             Remote SQL: SELECT "C 1", c2, c3, c4, c5, c6, c7, c8 FROM "S 1"."T 1" WHERE (("C 1" < 100))
+                                 ->  Sort
+                                       Output: ft2.*, ft2.c1, ft2.c2, (postgres_fdw_abs(ft2.c2))
+                                       Sort Key: (postgres_fdw_abs(ft2.c2)), ft2.c1
+                                       ->  Foreign Scan on public.ft2
+                                             Output: ft2.*, ft2.c1, ft2.c2, postgres_fdw_abs(ft2.c2)
+                                             Remote SQL: SELECT "C 1", c2, c3, c4, c5, c6, c7, c8 FROM "S 1"."T 1" ORDER BY "C 1" ASC NULLS LAST
+(32 rows)
+
+ALTER SERVER loopback OPTIONS (DROP fdw_startup_cost);
+ALTER SERVER loopback OPTIONS (ADD extensions 'postgres_fdw');
 DROP TABLE local_tbl;
 -- check join pushdown in situations where multiple userids are involved
 CREATE ROLE regress_view_owner SUPERUSER;

contrib/postgres_fdw/postgres_fdw.c

@@ -5784,6 +5784,55 @@ add_paths_with_pathkeys_for_rel(PlannerInfo *root, RelOptInfo *rel,
 
 	useful_pathkeys_list = get_useful_pathkeys_for_relation(root, rel);
 
+	/*
+	 * Before creating sorted paths, arrange for the passed-in EPQ path, if
+	 * any, to return columns needed by the parent ForeignScan node so that
+	 * they will propagate up through Sort nodes injected below, if necessary.
+	 */
+	if (epq_path != NULL && useful_pathkeys_list != NIL)
+	{
+		PgFdwRelationInfo *fpinfo = (PgFdwRelationInfo *) rel->fdw_private;
+		PathTarget *target = copy_pathtarget(epq_path->pathtarget);
+
+		/* Include columns required for evaluating PHVs in the tlist. */
+		add_new_columns_to_pathtarget(target,
+									  pull_var_clause((Node *) target->exprs,
+													  PVC_RECURSE_PLACEHOLDERS));
+
+		/* Include columns required for evaluating the local conditions. */
+		foreach(lc, fpinfo->local_conds)
+		{
+			RestrictInfo *rinfo = lfirst_node(RestrictInfo, lc);
+
+			add_new_columns_to_pathtarget(target,
+										  pull_var_clause((Node *) rinfo->clause,
+														  PVC_RECURSE_PLACEHOLDERS));
+		}
+
+		/*
+		 * If we have added any new columns, adjust the tlist of the EPQ path.
+		 *
+		 * Note: the plan created using this path will only be used to execute
+		 * EPQ checks, where accuracy of the plan cost and width estimates
+		 * would not be important, so we do not do set_pathtarget_cost_width()
+		 * for the new pathtarget here.  See also postgresGetForeignPlan().
+		 */
+		if (list_length(target->exprs) > list_length(epq_path->pathtarget->exprs))
+		{
+			/* The EPQ path is a join path, so it is projection-capable. */
+			Assert(is_projection_capable_path(epq_path));
+
+			/*
+			 * Use create_projection_path() here, so as to avoid modifying it
+			 * in place.
+			 */
+			epq_path = (Path *) create_projection_path(root,
+													   rel,
+													   epq_path,
+													   target);
+		}
+	}
+
 	/* Create one path for each set of pathkeys we found above. */
 	foreach(lc, useful_pathkeys_list)
 	{

contrib/postgres_fdw/sql/postgres_fdw.sql

@@ -672,6 +672,19 @@ SELECT * FROM ft1, ft2, ft4, ft5, local_tbl WHERE ft1.c1 = ft2.c1 AND ft1.c2 = f
     AND ft1.c2 = ft5.c1 AND ft1.c2 = local_tbl.c1 AND ft1.c1 < 100 AND ft2.c1 < 100 FOR UPDATE;
 RESET enable_nestloop;
 RESET enable_hashjoin;
+
+-- test that add_paths_with_pathkeys_for_rel() arranges for the epq_path to
+-- return columns needed by the parent ForeignScan node
+EXPLAIN (VERBOSE, COSTS OFF)
+SELECT * FROM local_tbl LEFT JOIN (SELECT ft1.*, COALESCE(ft1.c3 || ft2.c3, 'foobar') FROM ft1 INNER JOIN ft2 ON (ft1.c1 = ft2.c1 AND ft1.c1 < 100)) ss ON (local_tbl.c1 = ss.c1) ORDER BY local_tbl.c1 FOR UPDATE OF local_tbl;
+
+ALTER SERVER loopback OPTIONS (DROP extensions);
+ALTER SERVER loopback OPTIONS (ADD fdw_startup_cost '10000.0');
+EXPLAIN (VERBOSE, COSTS OFF)
+SELECT * FROM local_tbl LEFT JOIN (SELECT ft1.* FROM ft1 INNER JOIN ft2 ON (ft1.c1 = ft2.c1 AND ft1.c1 < 100 AND ft1.c1 = postgres_fdw_abs(ft2.c2))) ss ON (local_tbl.c3 = ss.c3) ORDER BY local_tbl.c1 FOR UPDATE OF local_tbl;
+ALTER SERVER loopback OPTIONS (DROP fdw_startup_cost);
+ALTER SERVER loopback OPTIONS (ADD extensions 'postgres_fdw');
+
 DROP TABLE local_tbl;
 
 -- check join pushdown in situations where multiple userids are involved