Replace TupleTableSlot convention for whole-row variables and function

results with tuples as ordinary varlena Datums.  This commit does not
in itself do much for us, except eliminate the horrid memory leak
associated with evaluation of whole-row variables.  However, it lays the
groundwork for allowing composite types as table columns, and perhaps
some other useful features as well.  Per my proposal of a few days ago.

src/include/access/tupdesc.h

@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2003, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/access/tupdesc.h,v 1.42 2003/11/29 22:40:55 pgsql Exp $
+ * $PostgreSQL: pgsql/src/include/access/tupdesc.h,v 1.43 2004/04/01 21:28:45 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -44,6 +44,15 @@ typedef struct tupleConstr
 /*
  * This structure contains all information (i.e. from Classes
  * pg_attribute, pg_attrdef, pg_constraint) for the structure of a tuple.
+ *
+ * Note that only user attributes, not system attributes, are mentioned in
+ * TupleDesc; with the exception that tdhasoid indicates if OID is present.
+ *
+ * If the tuple is known to correspond to a named rowtype (such as a table's
+ * rowtype) then tdtypeid identifies that type and tdtypmod is -1.  Otherwise
+ * tdtypeid is RECORDOID, and tdtypmod can be either -1 for a fully anonymous
+ * row type, or a value >= 0 to allow the rowtype to be looked up in the
+ * typcache.c type cache.
  */
 typedef struct tupleDesc
 {
@@ -51,6 +60,8 @@ typedef struct tupleDesc
 	Form_pg_attribute *attrs;
 	/* attrs[N] is a pointer to the description of Attribute Number N+1.  */
 	TupleConstr *constr;
+	Oid			tdtypeid;		/* composite type ID for tuple type */
+	int32		tdtypmod;		/* typmod for tuple type */
 	bool		tdhasoid;		/* Tuple has oid attribute in its header */
 }	*TupleDesc;
 
@@ -73,8 +84,7 @@ extern void TupleDescInitEntry(TupleDesc desc,
 				   const char *attributeName,
 				   Oid oidtypeid,
 				   int32 typmod,
-				   int attdim,
-				   bool attisset);
+				   int attdim);
 
 extern TupleDesc BuildDescForRelation(List *schema);