automatically add primary key to #select_limited_ids_list order by clause for...

automatically add primary key to #select_limited_ids_list order by clause for databases that require order columns in the distinct statements (postgresql) [Rick]

git-svn-id: http://svn-commit.rubyonrails.org/rails/trunk@5292 5ecf4fe2-1ee6-0310-87b1-e25e094e27de

activerecord/lib/active_record/associations.rb

@@ -1197,6 +1197,7 @@ def construct_finder_sql_for_association_limiting(options, join_dependency)
           sql = "SELECT "
           if is_distinct
             ordered_columns = options[:order].to_s.split(',').collect! { |s| s.split.first }
+            options[:order] = "#{table_name}.#{primary_key}, #{options[:order]}" if options[:order] && connection.requires_order_columns_in_distinct_clause?
             sql << connection.distinct("#{table_name}.#{primary_key}", ordered_columns)
           else
             sql << primary_key

activerecord/lib/active_record/connection_adapters/abstract_adapter.rb

@@ -56,6 +56,12 @@ def prefetch_primary_key?(table_name = nil)
         false
       end
 
+      # Does this adapter require the order columns to be in the select clause
+      # of a DISTINCT query?  This is +false+ in all adapters except postgresql.
+      def requires_order_columns_in_distinct_clause?
+        false
+      end
+
       def reset_runtime #:nodoc:
         rt, @runtime = @runtime, 0
         rt

activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb

@@ -111,6 +111,10 @@ def table_alias_length
         63
       end
 
+      def requires_order_columns_in_distinct_clause?
+        true
+      end
+
       # QUOTING ==================================================
 
       def quote(value, column = nil)

activerecord/test/associations_test.rb

@@ -1793,7 +1793,7 @@ def test_select_limited_ids_list
     
     join_base = ActiveRecord::Associations::ClassMethods::JoinDependency::JoinBase.new(Project)
     join_dep  = ActiveRecord::Associations::ClassMethods::JoinDependency.new(join_base, :developers, nil)
-    projects  = Project.send(:select_limited_ids_list, {:order => 'projects.id, developers.created_at'}, join_dep)
+    projects  = Project.send(:select_limited_ids_list, {:order => 'developers.created_at'}, join_dep)
     assert_equal "'1', '2'", projects
   end
 end