Build whole-row Vars the same way during parsing and planning.

makeWholeRowVar() has different rules for constructing a
whole-row Var depending on the kind of RTE it's representing.
This turns out to be problematic because the rewriter and planner
can convert view RTEs and set-returning-function RTEs into
subquery RTEs; so a whole-row Var made during planning might
look different from one made by the parser.  In isolation this
doesn't cause any problem, but if a query contains Vars made
both ways for the same varno, there are cross-checks in the
executor that will complain.  This manifests for UPDATE, DELETE,
and MERGE queries that use whole-row table references.

To fix, we need makeWholeRowVar() to produce the same result
from an inlined RTE as it would have for the original.  For
an inlined view, we can use RangeTblEntry.relid to detect
that this had been a view RTE.  For inlined SRFs, make a
data structure definition change akin to commit 47bb9db75,
and say that we won't clear RangeTblEntry.functions until
the end of planning.  That allows makeWholeRowVar() to
repeat what it would have done with the unmodified RTE.

Reported-by: Duncan Sands <duncan.sands@deepbluecap.com>
Reported-by: Dean Rasheed <dean.a.rasheed@gmail.com>
Diagnosed-by: Tender Wang <tndrwang@gmail.com>
Author: Tom Lane <tgl@sss.pgh.pa.us>
Reviewed-by: Dean Rasheed <dean.a.rasheed@gmail.com>
Discussion: https://postgr.es/m/3518c50a-ab18-482f-b916-a37263622501@deepbluecap.com
Backpatch-through: 13

src/backend/nodes/makefuncs.c

@@ -155,6 +155,53 @@ makeWholeRowVar(RangeTblEntry *rte,
 							 varlevelsup);
 			break;
 
+		case RTE_SUBQUERY:
+
+			/*
+			 * For a standard subquery, the Var should be of RECORD type.
+			 * However, if we're looking at a subquery that was expanded from
+			 * a view or SRF (only possible during planning), we must use the
+			 * appropriate rowtype, so that the resulting Var has the same
+			 * type that we would have produced from the original RTE.
+			 */
+			if (OidIsValid(rte->relid))
+			{
+				/* Subquery was expanded from a view */
+				toid = get_rel_type_id(rte->relid);
+				if (!OidIsValid(toid))
+					ereport(ERROR,
+							(errcode(ERRCODE_WRONG_OBJECT_TYPE),
+							 errmsg("relation \"%s\" does not have a composite type",
+									get_rel_name(rte->relid))));
+			}
+			else if (rte->functions)
+			{
+				/*
+				 * Subquery was expanded from a set-returning function.  That
+				 * would not have happened if there's more than one function
+				 * or ordinality was requested.  We also needn't worry about
+				 * the allowScalar case, since the planner doesn't use that.
+				 * Otherwise this must match the RTE_FUNCTION code below.
+				 */
+				Assert(!allowScalar);
+				fexpr = ((RangeTblFunction *) linitial(rte->functions))->funcexpr;
+				toid = exprType(fexpr);
+				if (!type_is_rowtype(toid))
+					toid = RECORDOID;
+			}
+			else
+			{
+				/* Normal subquery-in-FROM */
+				toid = RECORDOID;
+			}
+			result = makeVar(varno,
+							 InvalidAttrNumber,
+							 toid,
+							 -1,
+							 InvalidOid,
+							 varlevelsup);
+			break;
+
 		case RTE_FUNCTION:
 
 			/*
@@ -211,8 +258,8 @@ makeWholeRowVar(RangeTblEntry *rte,
 		default:
 
 			/*
-			 * RTE is a join, subselect, tablefunc, or VALUES.  We represent
-			 * this as a whole-row Var of RECORD type. (Note that in most
+			 * RTE is a join, tablefunc, VALUES, CTE, etc.  We represent these
+			 * cases as a whole-row Var of RECORD type.  (Note that in most
 			 * cases the Var will be expanded to a RowExpr during planning,
 			 * but that is not our concern here.)
 			 */

src/backend/optimizer/prep/prepjointree.c

@@ -668,8 +668,14 @@ preprocess_function_rtes(PlannerInfo *root)
 				rte->rtekind = RTE_SUBQUERY;
 				rte->subquery = funcquery;
 				rte->security_barrier = false;
-				/* Clear fields that should not be set in a subquery RTE */
-				rte->functions = NIL;
+
+				/*
+				 * Clear fields that should not be set in a subquery RTE.
+				 * However, we leave rte->functions filled in for the moment,
+				 * in case makeWholeRowVar needs to consult it.  We'll clear
+				 * it in setrefs.c (see add_rte_to_flat_rtable) so that this
+				 * abuse of the data structure doesn't escape the planner.
+				 */
 				rte->funcordinality = false;
 			}
 		}

src/test/regress/expected/returning.out

@@ -286,6 +286,63 @@ SELECT * FROM voo;
  16 | zoo2
 (2 rows)
 
+-- Check use of a whole-row variable for an un-flattenable view
+CREATE TEMP VIEW foo_v AS SELECT * FROM foo OFFSET 0;
+UPDATE foo SET f2 = foo_v.f2 FROM foo_v WHERE foo_v.f1 = foo.f1
+  RETURNING foo_v;
+      foo_v      
+-----------------
+ (2,more,42,141)
+ (16,zoo2,57,99)
+(2 rows)
+
+SELECT * FROM foo;
+ f1 |  f2  | f3 | f4  
+----+------+----+-----
+  2 | more | 42 | 141
+ 16 | zoo2 | 57 |  99
+(2 rows)
+
+-- Check use of a whole-row variable for an inlined set-returning function
+CREATE FUNCTION foo_f() RETURNS SETOF foo AS
+  $$ SELECT * FROM foo OFFSET 0 $$ LANGUAGE sql STABLE;
+UPDATE foo SET f2 = foo_f.f2 FROM foo_f() WHERE foo_f.f1 = foo.f1
+  RETURNING foo_f;
+      foo_f      
+-----------------
+ (2,more,42,141)
+ (16,zoo2,57,99)
+(2 rows)
+
+SELECT * FROM foo;
+ f1 |  f2  | f3 | f4  
+----+------+----+-----
+  2 | more | 42 | 141
+ 16 | zoo2 | 57 |  99
+(2 rows)
+
+DROP FUNCTION foo_f();
+-- As above, but SRF is defined to return a composite type
+CREATE TYPE foo_t AS (f1 int, f2 text, f3 int, f4 int8);
+CREATE FUNCTION foo_f() RETURNS SETOF foo_t AS
+  $$ SELECT * FROM foo OFFSET 0 $$ LANGUAGE sql STABLE;
+UPDATE foo SET f2 = foo_f.f2 FROM foo_f() WHERE foo_f.f1 = foo.f1
+  RETURNING foo_f;
+      foo_f      
+-----------------
+ (2,more,42,141)
+ (16,zoo2,57,99)
+(2 rows)
+
+SELECT * FROM foo;
+ f1 |  f2  | f3 | f4  
+----+------+----+-----
+  2 | more | 42 | 141
+ 16 | zoo2 | 57 |  99
+(2 rows)
+
+DROP FUNCTION foo_f();
+DROP TYPE foo_t;
 -- Try a join case
 CREATE TEMP TABLE joinme (f2j text, other int);
 INSERT INTO joinme VALUES('more', 12345);

src/test/regress/sql/returning.sql

@@ -132,6 +132,30 @@ DELETE FROM foo WHERE f2 = 'zit' RETURNING *;
 SELECT * FROM foo;
 SELECT * FROM voo;
 
+-- Check use of a whole-row variable for an un-flattenable view
+CREATE TEMP VIEW foo_v AS SELECT * FROM foo OFFSET 0;
+UPDATE foo SET f2 = foo_v.f2 FROM foo_v WHERE foo_v.f1 = foo.f1
+  RETURNING foo_v;
+SELECT * FROM foo;
+
+-- Check use of a whole-row variable for an inlined set-returning function
+CREATE FUNCTION foo_f() RETURNS SETOF foo AS
+  $$ SELECT * FROM foo OFFSET 0 $$ LANGUAGE sql STABLE;
+UPDATE foo SET f2 = foo_f.f2 FROM foo_f() WHERE foo_f.f1 = foo.f1
+  RETURNING foo_f;
+SELECT * FROM foo;
+DROP FUNCTION foo_f();
+
+-- As above, but SRF is defined to return a composite type
+CREATE TYPE foo_t AS (f1 int, f2 text, f3 int, f4 int8);
+CREATE FUNCTION foo_f() RETURNS SETOF foo_t AS
+  $$ SELECT * FROM foo OFFSET 0 $$ LANGUAGE sql STABLE;
+UPDATE foo SET f2 = foo_f.f2 FROM foo_f() WHERE foo_f.f1 = foo.f1
+  RETURNING foo_f;
+SELECT * FROM foo;
+DROP FUNCTION foo_f();
+DROP TYPE foo_t;
+
 -- Try a join case
 
 CREATE TEMP TABLE joinme (f2j text, other int);