Instead of supposing (wrongly, in the general case) that the rowtype

of an inheritance child table is binary-compatible with the rowtype of
its parent, invent an expression node type that does the conversion
correctly.  Fixes the new bug exhibited by Kris Shannon as well as a
lot of old bugs that would only show up when using multiple inheritance
or after altering the parent table.

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 1.293 2004/11/05 19:15:59 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/nodes/copyfuncs.c,v 1.294 2004/12/11 23:26:33 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -876,6 +876,21 @@ _copyRelabelType(RelabelType *from)
 	return newnode;
 }
 
+/*
+ * _copyConvertRowtypeExpr
+ */
+static ConvertRowtypeExpr *
+_copyConvertRowtypeExpr(ConvertRowtypeExpr *from)
+{
+	ConvertRowtypeExpr *newnode = makeNode(ConvertRowtypeExpr);
+
+	COPY_NODE_FIELD(arg);
+	COPY_SCALAR_FIELD(resulttype);
+	COPY_SCALAR_FIELD(convertformat);
+
+	return newnode;
+}
+
 /*
  * _copyCaseExpr
  */
@@ -2696,6 +2711,9 @@ copyObject(void *from)
 		case T_RelabelType:
 			retval = _copyRelabelType(from);
 			break;
+		case T_ConvertRowtypeExpr:
+			retval = _copyConvertRowtypeExpr(from);
+			break;
 		case T_CaseExpr:
 			retval = _copyCaseExpr(from);
 			break;

src/backend/nodes/equalfuncs.c

@@ -18,7 +18,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/nodes/equalfuncs.c,v 1.232 2004/11/05 19:15:59 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/nodes/equalfuncs.c,v 1.233 2004/12/11 23:26:33 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -380,6 +380,24 @@ _equalRelabelType(RelabelType *a, RelabelType *b)
 	return true;
 }
 
+static bool
+_equalConvertRowtypeExpr(ConvertRowtypeExpr *a, ConvertRowtypeExpr *b)
+{
+	COMPARE_NODE_FIELD(arg);
+	COMPARE_SCALAR_FIELD(resulttype);
+
+	/*
+	 * Special-case COERCE_DONTCARE, so that planner can build coercion
+	 * nodes that are equal() to both explicit and implicit coercions.
+	 */
+	if (a->convertformat != b->convertformat &&
+		a->convertformat != COERCE_DONTCARE &&
+		b->convertformat != COERCE_DONTCARE)
+		return false;
+
+	return true;
+}
+
 static bool
 _equalCaseExpr(CaseExpr *a, CaseExpr *b)
 {
@@ -1844,6 +1862,9 @@ equal(void *a, void *b)
 		case T_RelabelType:
 			retval = _equalRelabelType(a, b);
 			break;
+		case T_ConvertRowtypeExpr:
+			retval = _equalConvertRowtypeExpr(a, b);
+			break;
 		case T_CaseExpr:
 			retval = _equalCaseExpr(a, b);
 			break;

src/backend/nodes/outfuncs.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/nodes/outfuncs.c,v 1.243 2004/08/29 05:06:43 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/backend/nodes/outfuncs.c,v 1.244 2004/12/11 23:26:33 tgl Exp $
  *
  * NOTES
  *	  Every node type that can appear in stored rules' parsetrees *must*
@@ -767,6 +767,16 @@ _outRelabelType(StringInfo str, RelabelType *node)
 	WRITE_ENUM_FIELD(relabelformat, CoercionForm);
 }
 
+static void
+_outConvertRowtypeExpr(StringInfo str, ConvertRowtypeExpr *node)
+{
+	WRITE_NODE_TYPE("CONVERTROWTYPEEXPR");
+
+	WRITE_NODE_FIELD(arg);
+	WRITE_OID_FIELD(resulttype);
+	WRITE_ENUM_FIELD(convertformat, CoercionForm);
+}
+
 static void
 _outCaseExpr(StringInfo str, CaseExpr *node)
 {
@@ -1728,6 +1738,9 @@ _outNode(StringInfo str, void *obj)
 			case T_RelabelType:
 				_outRelabelType(str, obj);
 				break;
+			case T_ConvertRowtypeExpr:
+				_outConvertRowtypeExpr(str, obj);
+				break;
 			case T_CaseExpr:
 				_outCaseExpr(str, obj);
 				break;

src/backend/nodes/readfuncs.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/nodes/readfuncs.c,v 1.173 2004/08/29 04:12:33 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/backend/nodes/readfuncs.c,v 1.174 2004/12/11 23:26:34 tgl Exp $
  *
  * NOTES
  *	  Path and Plan nodes do not have any readfuncs support, because we
@@ -575,6 +575,21 @@ _readRelabelType(void)
 	READ_DONE();
 }
 
+/*
+ * _readConvertRowtypeExpr
+ */
+static ConvertRowtypeExpr *
+_readConvertRowtypeExpr(void)
+{
+	READ_LOCALS(ConvertRowtypeExpr);
+
+	READ_NODE_FIELD(arg);
+	READ_OID_FIELD(resulttype);
+	READ_ENUM_FIELD(convertformat, CoercionForm);
+
+	READ_DONE();
+}
+
 /*
  * _readCaseExpr
  */
@@ -971,6 +986,8 @@ parseNodeString(void)
 		return_value = _readFieldStore();
 	else if (MATCH("RELABELTYPE", 11))
 		return_value = _readRelabelType();
+	else if (MATCH("CONVERTROWTYPEEXPR", 18))
+		return_value = _readConvertRowtypeExpr();
 	else if (MATCH("CASE", 4))
 		return_value = _readCaseExpr();
 	else if (MATCH("WHEN", 4))