Zero-label enums:

Allow enums to be created with zero labels, for use during binary upgrade.

doc/src/sgml/ref/create_type.sgml

 <!--
-$PostgreSQL: pgsql/doc/src/sgml/ref/create_type.sgml,v 1.79 2008/11/30 19:01:29 tgl Exp $
+$PostgreSQL: pgsql/doc/src/sgml/ref/create_type.sgml,v 1.80 2009/12/26 16:55:21 momjian Exp $
 PostgreSQL documentation
 -->
 
@@ -25,7 +25,7 @@ CREATE TYPE <replaceable class="parameter">name</replaceable> AS
     ( <replaceable class="PARAMETER">attribute_name</replaceable> <replaceable class="PARAMETER">data_type</replaceable> [, ... ] )
 
 CREATE TYPE <replaceable class="parameter">name</replaceable> AS ENUM
-    ( '<replaceable class="parameter">label</replaceable>' [, ... ] )
+    ( [ '<replaceable class="parameter">label</replaceable>' [, ... ] ] )
 
 CREATE TYPE <replaceable class="parameter">name</replaceable> (
     INPUT = <replaceable class="parameter">input_function</replaceable>,

src/backend/parser/gram.y

@@ -11,7 +11,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/parser/gram.y,v 2.699 2009/12/23 17:41:43 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/parser/gram.y,v 2.700 2009/12/26 16:55:21 momjian Exp $
  *
  * HISTORY
  *	  AUTHOR			DATE			MAJOR EVENT
@@ -297,7 +297,7 @@ static TypeName *TableFuncTypeName(List *columns);
 				TableFuncElementList opt_type_modifiers
 				prep_type_clause
 				execute_param_clause using_clause returning_clause
-				enum_val_list table_func_column_list
+				opt_enum_val_list enum_val_list table_func_column_list
 				create_generic_options alter_generic_options
 				relation_expr_list dostmt_opt_list
 
@@ -3623,7 +3623,7 @@ DefineStmt:
 					n->coldeflist = $6;
 					$$ = (Node *)n;
 				}
-			| CREATE TYPE_P any_name AS ENUM_P '(' enum_val_list ')'
+			| CREATE TYPE_P any_name AS ENUM_P '(' opt_enum_val_list ')'
 				{
 					CreateEnumStmt *n = makeNode(CreateEnumStmt);
 					n->typeName = $3;
@@ -3715,6 +3715,11 @@ old_aggr_elem:  IDENT '=' def_arg
 				}
 		;
 
+opt_enum_val_list:
+		enum_val_list							{ $$ = $1; }
+		| /*EMPTY*/								{ $$ = NIL; }
+		;
+
 enum_val_list:	Sconst
 				{ $$ = list_make1(makeString($1)); }
 			| enum_val_list ',' Sconst

src/bin/pg_dump/pg_dump.c

@@ -12,7 +12,7 @@
  *	by PostgreSQL
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/bin/pg_dump/pg_dump.c,v 1.561 2009/12/24 22:09:23 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/bin/pg_dump/pg_dump.c,v 1.562 2009/12/26 16:55:21 momjian Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -6542,12 +6542,6 @@ dumpEnumType(Archive *fout, TypeInfo *tyinfo)
 	check_sql_result(res, g_conn, query->data, PGRES_TUPLES_OK);
 
 	num = PQntuples(res);
-	/* should be at least 1 value */
-	if (num == 0)
-	{
-		write_msg(NULL, "no label definitions found for enum ID %u\n", tyinfo->dobj.catId.oid);
-		exit_nicely();
-	}
 
 	/*
 	 * DROP must be fully qualified in case same name appears in pg_catalog.