When expanding a whole-row Var into a RowExpr during ResolveNew(), attach

the column alias names of the RTE referenced by the Var to the RowExpr.
This is needed to allow ruleutils.c to correctly deparse FieldSelect nodes
referencing such a construct.  Per my recent bug report.

Adding a field to RowExpr forces initdb (because of stored rules changes)
so this solution is not back-patchable; which is unfortunate because 8.2
and 8.3 have this issue.  But it only affects EXPLAIN for some pretty odd
corner cases, so we can probably live without a solution for the back
branches.

src/backend/nodes/copyfuncs.c

@@ -15,7 +15,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/nodes/copyfuncs.c,v 1.406 2008/10/04 21:56:53 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/nodes/copyfuncs.c,v 1.407 2008/10/06 17:39:25 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -1257,6 +1257,7 @@ _copyRowExpr(RowExpr *from)
 	COPY_NODE_FIELD(args);
 	COPY_SCALAR_FIELD(row_typeid);
 	COPY_SCALAR_FIELD(row_format);
+	COPY_NODE_FIELD(colnames);
 	COPY_LOCATION_FIELD(location);
 
 	return newnode;

src/backend/nodes/equalfuncs.c

@@ -22,7 +22,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/nodes/equalfuncs.c,v 1.332 2008/10/04 21:56:53 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/nodes/equalfuncs.c,v 1.333 2008/10/06 17:39:26 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -511,6 +511,7 @@ _equalRowExpr(RowExpr *a, RowExpr *b)
 		b->row_format != COERCE_DONTCARE)
 		return false;
 
+	COMPARE_NODE_FIELD(colnames);
 	COMPARE_LOCATION_FIELD(location);
 
 	return true;

src/backend/nodes/nodeFuncs.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/nodes/nodeFuncs.c,v 1.33 2008/10/04 21:56:53 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/nodes/nodeFuncs.c,v 1.34 2008/10/06 17:39:26 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -1172,6 +1172,7 @@ expression_tree_walker(Node *node,
 		case T_ArrayExpr:
 			return walker(((ArrayExpr *) node)->elements, context);
 		case T_RowExpr:
+			/* Assume colnames isn't interesting */
 			return walker(((RowExpr *) node)->args, context);
 		case T_RowCompareExpr:
 			{
@@ -1735,6 +1736,7 @@ expression_tree_mutator(Node *node,
 
 				FLATCOPY(newnode, rowexpr, RowExpr);
 				MUTATE(newnode->args, rowexpr->args, List *);
+				/* Assume colnames needn't be duplicated */
 				return (Node *) newnode;
 			}
 			break;
@@ -2174,6 +2176,7 @@ raw_expression_tree_walker(Node *node, bool (*walker) (), void *context)
 			}
 			break;
 		case T_RowExpr:
+			/* Assume colnames isn't interesting */
 			return walker(((RowExpr *) node)->args, context);
 		case T_CoalesceExpr:
 			return walker(((CoalesceExpr *) node)->args, context);

src/backend/nodes/outfuncs.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/nodes/outfuncs.c,v 1.340 2008/10/04 21:56:53 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/nodes/outfuncs.c,v 1.341 2008/10/06 17:39:26 tgl Exp $
  *
  * NOTES
  *	  Every node type that can appear in stored rules' parsetrees *must*
@@ -1037,6 +1037,7 @@ _outRowExpr(StringInfo str, RowExpr *node)
 	WRITE_NODE_FIELD(args);
 	WRITE_OID_FIELD(row_typeid);
 	WRITE_ENUM_FIELD(row_format, CoercionForm);
+	WRITE_NODE_FIELD(colnames);
 	WRITE_LOCATION_FIELD(location);
 }
 

src/backend/nodes/readfuncs.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/nodes/readfuncs.c,v 1.215 2008/10/04 21:56:53 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/nodes/readfuncs.c,v 1.216 2008/10/06 17:39:26 tgl Exp $
  *
  * NOTES
  *	  Path and Plan nodes do not have any readfuncs support, because we
@@ -744,6 +744,7 @@ _readRowExpr(void)
 	READ_NODE_FIELD(args);
 	READ_OID_FIELD(row_typeid);
 	READ_ENUM_FIELD(row_format, CoercionForm);
+	READ_NODE_FIELD(colnames);
 	READ_LOCATION_FIELD(location);
 
 	READ_DONE();

src/backend/optimizer/prep/prepunion.c

@@ -22,7 +22,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/optimizer/prep/prepunion.c,v 1.156 2008/10/04 21:56:53 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/optimizer/prep/prepunion.c,v 1.157 2008/10/06 17:39:26 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -1493,6 +1493,7 @@ adjust_appendrel_attrs_mutator(Node *node, AppendRelInfo *context)
 					rowexpr->args = fields;
 					rowexpr->row_typeid = var->vartype;
 					rowexpr->row_format = COERCE_IMPLICIT_CAST;
+					rowexpr->colnames = NIL;
 					rowexpr->location = -1;
 
 					return (Node *) rowexpr;

src/backend/optimizer/util/var.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/optimizer/util/var.c,v 1.79 2008/09/01 20:42:44 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/optimizer/util/var.c,v 1.80 2008/10/06 17:39:26 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -663,6 +663,7 @@ flatten_join_alias_vars_mutator(Node *node,
 			rowexpr->args = fields;
 			rowexpr->row_typeid = var->vartype;
 			rowexpr->row_format = COERCE_IMPLICIT_CAST;
+			rowexpr->colnames = NIL;
 			rowexpr->location = -1;
 
 			return (Node *) rowexpr;

src/backend/parser/parse_coerce.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/parser/parse_coerce.c,v 2.167 2008/09/10 18:29:40 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/parser/parse_coerce.c,v 2.168 2008/10/06 17:39:26 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -926,6 +926,7 @@ coerce_record_to_complex(ParseState *pstate, Node *node,
 	rowexpr->args = newargs;
 	rowexpr->row_typeid = targetTypeId;
 	rowexpr->row_format = cformat;
+	rowexpr->colnames = NIL;	/* not needed for named target type */
 	rowexpr->location = location;
 	return (Node *) rowexpr;
 }

src/backend/parser/parse_expr.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/parser/parse_expr.c,v 1.234 2008/09/01 20:42:44 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/parser/parse_expr.c,v 1.235 2008/10/06 17:39:26 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -1534,6 +1534,7 @@ transformRowExpr(ParseState *pstate, RowExpr *r)
 	/* Barring later casting, we consider the type RECORD */
 	newr->row_typeid = RECORDOID;
 	newr->row_format = COERCE_IMPLICIT_CAST;
+	newr->colnames = NIL;		/* ROW() has anonymous columns */
 	newr->location = r->location;
 
 	return (Node *) newr;

src/backend/rewrite/rewriteManip.c

@@ -7,7 +7,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/rewrite/rewriteManip.c,v 1.114 2008/10/04 21:56:54 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/rewrite/rewriteManip.c,v 1.115 2008/10/06 17:39:26 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -1057,18 +1057,20 @@ ResolveNew_mutator(Node *node, ResolveNew_context *context)
 			{
 				/* Must expand whole-tuple reference into RowExpr */
 				RowExpr    *rowexpr;
+				List	   *colnames;
 				List	   *fields;
 
 				/*
 				 * If generating an expansion for a var of a named rowtype
 				 * (ie, this is a plain relation RTE), then we must include
 				 * dummy items for dropped columns.  If the var is RECORD (ie,
-				 * this is a JOIN), then omit dropped columns.
+				 * this is a JOIN), then omit dropped columns.  Either way,
+				 * attach column names to the RowExpr for use of ruleutils.c.
 				 */
 				expandRTE(context->target_rte,
 						  this_varno, this_varlevelsup, var->location,
 						  (var->vartype != RECORDOID),
-						  NULL, &fields);
+						  &colnames, &fields);
 				/* Adjust the generated per-field Vars... */
 				fields = (List *) ResolveNew_mutator((Node *) fields,
 													 context);
@@ -1076,6 +1078,7 @@ ResolveNew_mutator(Node *node, ResolveNew_context *context)
 				rowexpr->args = fields;
 				rowexpr->row_typeid = var->vartype;
 				rowexpr->row_format = COERCE_IMPLICIT_CAST;
+				rowexpr->colnames = colnames;
 				rowexpr->location = -1;
 
 				return (Node *) rowexpr;

src/backend/utils/adt/ruleutils.c

@@ -9,7 +9,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/utils/adt/ruleutils.c,v 1.285 2008/10/04 21:56:54 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/utils/adt/ruleutils.c,v 1.286 2008/10/06 17:39:26 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -3236,6 +3236,18 @@ get_name_for_var_field(Var *var, int fieldno,
 	TupleDesc	tupleDesc;
 	Node	   *expr;
 
+	/*
+	 * If it's a RowExpr that was expanded from a whole-row Var, use the
+	 * column names attached to it.
+	 */
+	if (IsA(var, RowExpr))
+	{
+		RowExpr	   *r = (RowExpr *) var;
+
+		if (fieldno > 0 && fieldno <= list_length(r->colnames))
+			return strVal(list_nth(r->colnames, fieldno - 1));
+	}
+
 	/*
 	 * If it's a Var of type RECORD, we have to find what the Var refers to;
 	 * if not, we can use get_expr_result_type. If that fails, we try

src/include/catalog/catversion.h

@@ -37,7 +37,7 @@
  * Portions Copyright (c) 1996-2008, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/catalog/catversion.h,v 1.495 2008/10/06 14:13:17 heikki Exp $
+ * $PostgreSQL: pgsql/src/include/catalog/catversion.h,v 1.496 2008/10/06 17:39:26 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -53,6 +53,6 @@
  */
 
 /*							yyyymmddN */
-#define CATALOG_VERSION_NO	200810062
+#define CATALOG_VERSION_NO	200810063
 
 #endif

src/include/nodes/primnodes.h

@@ -10,7 +10,7 @@
  * Portions Copyright (c) 1996-2008, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/nodes/primnodes.h,v 1.142 2008/10/04 21:56:55 tgl Exp $
+ * $PostgreSQL: pgsql/src/include/nodes/primnodes.h,v 1.143 2008/10/06 17:39:26 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -740,6 +740,12 @@ typedef struct ArrayExpr
  * not RECORD types, since those are built from the RowExpr itself rather
  * than vice versa.)  It is important not to assume that length(args) is
  * the same as the number of columns logically present in the rowtype.
+ *
+ * colnames is NIL in a RowExpr built from an ordinary ROW() expression.
+ * It is provided in cases where we expand a whole-row Var into a RowExpr,
+ * to retain the column alias names of the RTE that the Var referenced
+ * (which would otherwise be very difficult to extract from the parsetree).
+ * Like the args list, it is one-for-one with physical fields of the rowtype.
  */
 typedef struct RowExpr
 {
@@ -754,6 +760,7 @@ typedef struct RowExpr
 	 * parsetrees.	We must assume typmod -1 for a RowExpr node.
 	 */
 	CoercionForm row_format;	/* how to display this node */
+	List	   *colnames;		/* list of String, or NIL */
 	int			location;		/* token location, or -1 if unknown */
 } RowExpr;