Allow CREATE FUNCTION xyz AS '' LANGUAGE 'internal' to

work the way it used to (ie, assume xyz is the name of the builtin
function to call).  Complain if an unknown builtin function name is
referenced.

src/backend/catalog/pg_proc.c

@@ -7,7 +7,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/catalog/pg_proc.c,v 1.26 1999/02/21 03:48:32 scrappy Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/catalog/pg_proc.c,v 1.27 1999/04/18 02:57:22 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -26,6 +26,7 @@
 #include "parser/parse_node.h"
 #include "tcop/tcopprot.h"
 #include "utils/builtins.h"
+#include "utils/fmgrtab.h"
 #include "utils/lsyscache.h"
 #include "utils/sets.h"
 #include "utils/syscache.h"
@@ -37,7 +38,7 @@
 #endif
 
 /* ----------------------------------------------------------------
- *		ProcedureDefine
+ *		ProcedureCreate
  * ----------------------------------------------------------------
  */
 Oid
@@ -94,7 +95,7 @@ ProcedureCreate(char *procedureName,
 		if (strcmp(strVal(t), "opaque") == 0)
 		{
 			if (strcmp(languageName, "sql") == 0)
-				elog(ERROR, "ProcedureDefine: sql functions cannot take type \"opaque\"");
+				elog(ERROR, "ProcedureCreate: sql functions cannot take type \"opaque\"");
 			toid = 0;
 		}
 		else
@@ -220,6 +221,32 @@ ProcedureCreate(char *procedureName,
 		pg_checkretval(typeObjectId, querytree_list);
 	}
 
+	/*
+	 * If this is an internal procedure, check that the given internal
+	 * function name (the 'prosrc' value) is a known builtin function.
+	 *
+	 * NOTE: in Postgres versions before 6.5, the SQL name of the created
+	 * function could not be different from the internal name, and 'prosrc'
+	 * wasn't used.  So there is code out there that does CREATE FUNCTION
+	 * xyz AS '' LANGUAGE 'internal'.  To preserve some modicum of
+	 * backwards compatibility, accept an empty 'prosrc' value as meaning
+	 * the supplied SQL function name.
+	 */
+
+	if (strcmp(languageName, "internal") == 0)
+	{
+		if (strlen(prosrc) == 0)
+			prosrc = procedureName;
+		if (fmgr_lookupByName(prosrc) == (func_ptr) NULL)
+			elog(ERROR,
+				 "ProcedureCreate: there is no builtin function named \"%s\"",
+				 prosrc);
+	}
+
+	/*
+	 * All seems OK; prepare the tuple to be inserted into pg_proc.
+	 */
+
 	for (i = 0; i < Natts_pg_proc; ++i)
 	{
 		nulls[i] = ' ';