Fixed columns_for_distinct of postgresql adapter

activerecord/CHANGELOG.md

@@ -1,3 +1,8 @@
+*   Fixed `columns_for_distinct` of postgresql adapter to work correctly
+    with orders without sort direction modifiers.
+
+    *Nikolay Kondratyev*
+
 *   Assign inet/cidr attribute with `nil` value for invalid address.
 
     Example:

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

@@ -475,7 +475,7 @@ def columns_for_distinct(columns, orders) #:nodoc:
               # Convert Arel node to string
               s = s.to_sql unless s.is_a?(String)
               # Remove any ASC/DESC modifiers
-              s.gsub(/\s+(ASC|DESC)\s*(NULLS\s+(FIRST|LAST)\s*)?/i, '')
+              s.gsub(/\s+(?:ASC|DESC)?\s*(?:NULLS\s+(?:FIRST|LAST)\s*)?/i, '')
             }.reject(&:blank?).map.with_index { |column, i| "#{column} AS alias_#{i}" }
 
           [super, *order_columns].join(', ')

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

@@ -259,6 +259,17 @@ def test_columns_for_distinct_with_nulls
         assert_equal "posts.title, posts.updater_id AS alias_0", @connection.columns_for_distinct("posts.title", ["posts.updater_id desc nulls last"])
       end
 
+      def test_columns_for_distinct_without_order_specifiers
+        assert_equal "posts.title, posts.updater_id AS alias_0",
+          @connection.columns_for_distinct("posts.title", ["posts.updater_id"])
+
+        assert_equal "posts.title, posts.updater_id AS alias_0",
+          @connection.columns_for_distinct("posts.title", ["posts.updater_id nulls last"])
+
+        assert_equal "posts.title, posts.updater_id AS alias_0",
+          @connection.columns_for_distinct("posts.title", ["posts.updater_id nulls first"])
+      end
+
       def test_raise_error_when_cannot_translate_exception
         assert_raise TypeError do
           @connection.send(:log, nil) { @connection.execute(nil) }