Fix planner's row-mark code for inheritance from a foreign table.

Commit 428b260f8 broke planning of cases where row marks are needed
(SELECT FOR UPDATE, etc) and one of the query's tables is a foreign
table that has regular table(s) as inheritance children.  We got the
reverse case right, but apparently were thinking that foreign tables
couldn't be inheritance parents.  Not so; so we need to be able to
add a CTID junk column while adding a new child, not only a wholerow
junk column.

Back-patch to v12 where the faulty code came in.

Amit Langote

Discussion: https://postgr.es/m/CA+HiwqEmo3FV1LAQ4TVyS2h1WM=kMkZUmbNuZSCnfHvMcUcPeA@mail.gmail.com

contrib/postgres_fdw/expected/postgres_fdw.out

@@ -7255,6 +7255,92 @@ select * from bar where f1 in (select f1 from foo) for share;
   4 | 44
 (4 rows)
 
+-- Now check SELECT FOR UPDATE/SHARE with an inherited source table,
+-- where the parent is itself a foreign table
+create table loct4 (f1 int, f2 int, f3 int);
+create foreign table foo2child (f3 int) inherits (foo2)
+  server loopback options (table_name 'loct4');
+NOTICE:  moving and merging column "f3" with inherited definition
+DETAIL:  User-specified column moved to the position of the inherited column.
+explain (verbose, costs off)
+select * from bar where f1 in (select f1 from foo2) for share;
+                                      QUERY PLAN                                      
+--------------------------------------------------------------------------------------
+ LockRows
+   Output: bar.f1, bar.f2, bar.ctid, foo2.*, bar.*, bar.tableoid, foo2.tableoid
+   ->  Hash Join
+         Output: bar.f1, bar.f2, bar.ctid, foo2.*, bar.*, bar.tableoid, foo2.tableoid
+         Inner Unique: true
+         Hash Cond: (bar.f1 = foo2.f1)
+         ->  Append
+               ->  Seq Scan on public.bar bar_1
+                     Output: bar_1.f1, bar_1.f2, bar_1.ctid, bar_1.*, bar_1.tableoid
+               ->  Foreign Scan on public.bar2 bar_2
+                     Output: bar_2.f1, bar_2.f2, bar_2.ctid, bar_2.*, bar_2.tableoid
+                     Remote SQL: SELECT f1, f2, f3, ctid FROM public.loct2 FOR SHARE
+         ->  Hash
+               Output: foo2.*, foo2.f1, foo2.tableoid
+               ->  HashAggregate
+                     Output: foo2.*, foo2.f1, foo2.tableoid
+                     Group Key: foo2.f1
+                     ->  Append
+                           ->  Foreign Scan on public.foo2 foo2_1
+                                 Output: foo2_1.*, foo2_1.f1, foo2_1.tableoid
+                                 Remote SQL: SELECT f1, f2, f3 FROM public.loct1
+                           ->  Foreign Scan on public.foo2child foo2_2
+                                 Output: foo2_2.*, foo2_2.f1, foo2_2.tableoid
+                                 Remote SQL: SELECT f1, f2, f3 FROM public.loct4
+(24 rows)
+
+select * from bar where f1 in (select f1 from foo2) for share;
+ f1 | f2 
+----+----
+  2 | 22
+  4 | 44
+(2 rows)
+
+drop foreign table foo2child;
+-- And with a local child relation of the foreign table parent
+create table foo2child (f3 int) inherits (foo2);
+NOTICE:  moving and merging column "f3" with inherited definition
+DETAIL:  User-specified column moved to the position of the inherited column.
+explain (verbose, costs off)
+select * from bar where f1 in (select f1 from foo2) for share;
+                                           QUERY PLAN                                            
+-------------------------------------------------------------------------------------------------
+ LockRows
+   Output: bar.f1, bar.f2, bar.ctid, foo2.*, bar.*, bar.tableoid, foo2.ctid, foo2.tableoid
+   ->  Hash Join
+         Output: bar.f1, bar.f2, bar.ctid, foo2.*, bar.*, bar.tableoid, foo2.ctid, foo2.tableoid
+         Inner Unique: true
+         Hash Cond: (bar.f1 = foo2.f1)
+         ->  Append
+               ->  Seq Scan on public.bar bar_1
+                     Output: bar_1.f1, bar_1.f2, bar_1.ctid, bar_1.*, bar_1.tableoid
+               ->  Foreign Scan on public.bar2 bar_2
+                     Output: bar_2.f1, bar_2.f2, bar_2.ctid, bar_2.*, bar_2.tableoid
+                     Remote SQL: SELECT f1, f2, f3, ctid FROM public.loct2 FOR SHARE
+         ->  Hash
+               Output: foo2.*, foo2.f1, foo2.ctid, foo2.tableoid
+               ->  HashAggregate
+                     Output: foo2.*, foo2.f1, foo2.ctid, foo2.tableoid
+                     Group Key: foo2.f1
+                     ->  Append
+                           ->  Foreign Scan on public.foo2 foo2_1
+                                 Output: foo2_1.*, foo2_1.f1, foo2_1.ctid, foo2_1.tableoid
+                                 Remote SQL: SELECT f1, f2, f3, ctid FROM public.loct1
+                           ->  Seq Scan on public.foo2child foo2_2
+                                 Output: foo2_2.*, foo2_2.f1, foo2_2.ctid, foo2_2.tableoid
+(23 rows)
+
+select * from bar where f1 in (select f1 from foo2) for share;
+ f1 | f2 
+----+----
+  2 | 22
+  4 | 44
+(2 rows)
+
+drop table foo2child;
 -- Check UPDATE with inherited target and an inherited source table
 explain (verbose, costs off)
 update bar set f2 = f2 + 100 where f1 in (select f1 from foo);

contrib/postgres_fdw/sql/postgres_fdw.sql

@@ -1891,6 +1891,27 @@ explain (verbose, costs off)
 select * from bar where f1 in (select f1 from foo) for share;
 select * from bar where f1 in (select f1 from foo) for share;
 
+-- Now check SELECT FOR UPDATE/SHARE with an inherited source table,
+-- where the parent is itself a foreign table
+create table loct4 (f1 int, f2 int, f3 int);
+create foreign table foo2child (f3 int) inherits (foo2)
+  server loopback options (table_name 'loct4');
+
+explain (verbose, costs off)
+select * from bar where f1 in (select f1 from foo2) for share;
+select * from bar where f1 in (select f1 from foo2) for share;
+
+drop foreign table foo2child;
+
+-- And with a local child relation of the foreign table parent
+create table foo2child (f3 int) inherits (foo2);
+
+explain (verbose, costs off)
+select * from bar where f1 in (select f1 from foo2) for share;
+select * from bar where f1 in (select f1 from foo2) for share;
+
+drop table foo2child;
+
 -- Check UPDATE with inherited target and an inherited source table
 explain (verbose, costs off)
 update bar set f2 = f2 + 100 where f1 in (select f1 from foo);

src/backend/optimizer/util/inherit.c

@@ -232,8 +232,25 @@ expand_inherited_rtentry(PlannerInfo *root, RelOptInfo *rel,
 		char		resname[32];
 		List	   *newvars = NIL;
 
-		/* The old PlanRowMark should already have necessitated adding TID */
-		Assert(old_allMarkTypes & ~(1 << ROW_MARK_COPY));
+		/* Add TID junk Var if needed, unless we had it already */
+		if (new_allMarkTypes & ~(1 << ROW_MARK_COPY) &&
+			!(old_allMarkTypes & ~(1 << ROW_MARK_COPY)))
+		{
+			/* Need to fetch TID */
+			var = makeVar(oldrc->rti,
+						  SelfItemPointerAttributeNumber,
+						  TIDOID,
+						  -1,
+						  InvalidOid,
+						  0);
+			snprintf(resname, sizeof(resname), "ctid%u", oldrc->rowmarkId);
+			tle = makeTargetEntry((Expr *) var,
+								  list_length(root->processed_tlist) + 1,
+								  pstrdup(resname),
+								  true);
+			root->processed_tlist = lappend(root->processed_tlist, tle);
+			newvars = lappend(newvars, var);
+		}
 
 		/* Add whole-row junk Var if needed, unless we had it already */
 		if ((new_allMarkTypes & (1 << ROW_MARK_COPY)) &&