Fix oversight in recent MULTIEXPR_SUBLINK fix.

Commits 3f7323cbb et al missed the possibility that the Params
they are looking for could be buried under implicit coercions,
as well as other stuff that processIndirection() could add to
the original targetlist entry.  Copy the code in ruleutils.c
that deals with such cases.  (I thought about refactoring so
that there's just one copy; but seeing that we only need this
in old back branches, it seems not worth the trouble.)

Per off-list report from Andre Lin.  As before, only v10-v13
need the patch.

Discussion: https://postgr.es/m/17596-c5357f61427a81dc@postgresql.org

src/backend/optimizer/plan/subselect.c

@@ -914,20 +914,54 @@ SS_make_multiexprs_unique(PlannerInfo *root, PlannerInfo *subroot)
 	/*
 	 * Now we must find the Param nodes that reference the MULTIEXPR outputs
 	 * and update their sublink IDs so they'll reference the new outputs.
-	 * Fortunately, those too must be at top level of the cloned targetlist.
+	 * Fortunately, those too must be in the cloned targetlist, but they could
+	 * be buried under FieldStores and SubscriptingRefs and CoerceToDomains
+	 * (cf processIndirection()), and underneath those there could be an
+	 * implicit type coercion.
 	 */
 	offset = list_length(root->multiexpr_params);
 
 	foreach(lc, subroot->parse->targetList)
 	{
 		TargetEntry *tent = (TargetEntry *) lfirst(lc);
+		Node	   *expr;
 		Param	   *p;
 		int			subqueryid;
 		int			colno;
 
-		if (!IsA(tent->expr, Param))
+		expr = (Node *) tent->expr;
+		while (expr)
+		{
+			if (IsA(expr, FieldStore))
+			{
+				FieldStore *fstore = (FieldStore *) expr;
+
+				expr = (Node *) linitial(fstore->newvals);
+			}
+			else if (IsA(expr, SubscriptingRef))
+			{
+				SubscriptingRef *sbsref = (SubscriptingRef *) expr;
+
+				if (sbsref->refassgnexpr == NULL)
+					break;
+
+				expr = (Node *) sbsref->refassgnexpr;
+			}
+			else if (IsA(expr, CoerceToDomain))
+			{
+				CoerceToDomain *cdomain = (CoerceToDomain *) expr;
+
+				if (cdomain->coercionformat != COERCE_IMPLICIT_CAST)
+					break;
+				expr = (Node *) cdomain->arg;
+			}
+			else
+				break;
+		}
+		expr = strip_implicit_coercions(expr);
+		if (expr == NULL || !IsA(expr, Param))
 			continue;
-		p = (Param *) tent->expr;
+		p = (Param *) expr;
 		if (p->paramkind != PARAM_MULTIEXPR)
 			continue;
 		subqueryid = p->paramid >> 16;

src/test/regress/expected/inherit.out

@@ -1717,48 +1717,48 @@ reset enable_bitmapscan;
 --
 -- Check handling of MULTIEXPR SubPlans in inherited updates
 --
-create table inhpar(f1 int, f2 name);
+create table inhpar(f1 int, f2 text[]);
 insert into inhpar select generate_series(1,10);
 create table inhcld() inherits(inhpar);
 insert into inhcld select generate_series(11,10000);
 vacuum analyze inhcld;
 vacuum analyze inhpar;
 explain (verbose, costs off)
-update inhpar set (f1, f2) = (select p2.unique2, p2.stringu1
+update inhpar set (f1, f2[1]) = (select p2.unique2, p2.stringu1
                                  from int4_tbl limit 1)
 from onek p2 where inhpar.f1 = p2.unique1;
                                           QUERY PLAN                                           
------------------------------------------------------------------------------
+-----------------------------------------------------------------------------------------------
  Update on public.inhpar
    Update on public.inhpar
    Update on public.inhcld inhpar_1
    ->  Merge Join
-         Output: $4, $5, (SubPlan 1 (returns $2,$3)), inhpar.ctid, p2.ctid
+         Output: $4, inhpar.f2[1] := $5, (SubPlan 1 (returns $2,$3)), inhpar.ctid, p2.ctid
          Merge Cond: (p2.unique1 = inhpar.f1)
          ->  Index Scan using onek_unique1 on public.onek p2
                Output: p2.unique2, p2.stringu1, p2.ctid, p2.unique1
          ->  Sort
-               Output: inhpar.ctid, inhpar.f1
+               Output: inhpar.f2, inhpar.ctid, inhpar.f1
                Sort Key: inhpar.f1
                ->  Seq Scan on public.inhpar
-                     Output: inhpar.ctid, inhpar.f1
+                     Output: inhpar.f2, inhpar.ctid, inhpar.f1
          SubPlan 1 (returns $2,$3)
            ->  Limit
                  Output: (p2.unique2), (p2.stringu1)
                  ->  Seq Scan on public.int4_tbl
                        Output: p2.unique2, p2.stringu1
    ->  Hash Join
-         Output: $6, $7, (SubPlan 1 (returns $2,$3)), inhpar_1.ctid, p2.ctid
+         Output: $6, inhpar_1.f2[1] := $7, (SubPlan 1 (returns $2,$3)), inhpar_1.ctid, p2.ctid
          Hash Cond: (inhpar_1.f1 = p2.unique1)
          ->  Seq Scan on public.inhcld inhpar_1
-               Output: inhpar_1.ctid, inhpar_1.f1
+               Output: inhpar_1.f2, inhpar_1.ctid, inhpar_1.f1
          ->  Hash
                Output: p2.unique2, p2.stringu1, p2.ctid, p2.unique1
                ->  Seq Scan on public.onek p2
                      Output: p2.unique2, p2.stringu1, p2.ctid, p2.unique1
 (27 rows)
 
-update inhpar set (f1, f2) = (select p2.unique2, p2.stringu1
+update inhpar set (f1, f2[1]) = (select p2.unique2, p2.stringu1
                                  from int4_tbl limit 1)
 from onek p2 where inhpar.f1 = p2.unique1;
 drop table inhpar cascade;

src/test/regress/sql/inherit.sql

@@ -632,7 +632,7 @@ reset enable_bitmapscan;
 --
 -- Check handling of MULTIEXPR SubPlans in inherited updates
 --
-create table inhpar(f1 int, f2 name);
+create table inhpar(f1 int, f2 text[]);
 insert into inhpar select generate_series(1,10);
 create table inhcld() inherits(inhpar);
 insert into inhcld select generate_series(11,10000);
@@ -640,10 +640,10 @@ vacuum analyze inhcld;
 vacuum analyze inhpar;
 
 explain (verbose, costs off)
-update inhpar set (f1, f2) = (select p2.unique2, p2.stringu1
+update inhpar set (f1, f2[1]) = (select p2.unique2, p2.stringu1
                                  from int4_tbl limit 1)
 from onek p2 where inhpar.f1 = p2.unique1;
-update inhpar set (f1, f2) = (select p2.unique2, p2.stringu1
+update inhpar set (f1, f2[1]) = (select p2.unique2, p2.stringu1
                                  from int4_tbl limit 1)
 from onek p2 where inhpar.f1 = p2.unique1;