Add Enum type to postgresql adapter's oids to prevent unknown OID warnings.

activerecord/CHANGELOG.md

+*   Dynamically register PostgreSQL enum OIDs. This prevents "unknown OID"
+    warnings on enum columns.
+
+    *Dieter Komendera*
+
 *   `includes` is able to detect the right preloading strategy when string
     joins are involved.
 

activerecord/lib/active_record/connection_adapters/postgresql/oid.rb

@@ -229,6 +229,12 @@ def infinity(options = {})
           end
         end
 
+        class Enum < Type
+          def type_cast(value)
+            value.to_s
+          end
+        end
+
         class Hstore < Type
           def type_cast_for_write(value)
             ConnectionAdapters::PostgreSQLColumn.hstore_to_string value

activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb

@@ -801,6 +801,12 @@ def initialize_type_map(type_map)
           leaves, nodes = nodes.partition { |row| row['typelem'] == '0' }
           arrays, nodes = nodes.partition { |row| row['typinput'] == 'array_in' }
 
+          # populate the enum types
+          enums, leaves = leaves.partition { |row| row['typinput'] == 'enum_in' }
+          enums.each do |row|
+            type_map[row['oid'].to_i] = OID::Enum.new
+          end
+
           # populate the base types
           leaves.find_all { |row| OID.registered_type? row['typname'] }.each do |row|
             type_map[row['oid'].to_i] = OID::NAMES[row['typname']]

activerecord/test/cases/adapters/postgresql/enum_test.rb

@@ -23,6 +23,8 @@ def setup
         t.column :current_mood, :mood
       end
     end
+    # reload type map after creating the enum type
+    @connection.send(:reload_type_map)
   end
 
   def test_enum_mapping
@@ -35,4 +37,30 @@ def test_enum_mapping
 
     assert_equal "happy", enum.reload.current_mood
   end
+
+  def test_invalid_enum_update
+    @connection.execute "INSERT INTO postgresql_enums VALUES (1, 'sad');"
+    enum = PostgresqlEnum.first
+    enum.current_mood = "angry"
+
+    assert_raise ActiveRecord::StatementInvalid do
+      enum.save
+    end
+  end
+
+  def test_no_oid_warning
+    @connection.execute "INSERT INTO postgresql_enums VALUES (1, 'sad');"
+    stderr_output = capture(:stderr) {
+        enum = PostgresqlEnum.first
+    }
+
+    assert stderr_output.blank?
+  end
+
+  def test_enum_type_cast
+    enum = PostgresqlEnum.new
+    enum.current_mood = :happy
+
+    assert_equal "happy", enum.current_mood
+  end
 end