removing parameter requirement for matching_attributes

lib/arel/algebra/relations/relation.rb

@@ -197,19 +197,5 @@ def taken;                  nil         end
     def skipped;                nil         end
     def sources;                []          end
     def locked;                 []          end
-
-    private
-    def matching_attributes(attribute)
-      unless @matching_attributes
-        @matching_attributes = Hash[attributes.map do |a|
-          [a.root, a]
-        end]
-      end
-      [@matching_attributes[attribute.root]] || []
-    end
-
-    def has_attribute?(attribute)
-      !matching_attributes(attribute).empty?
-    end
   end
 end

lib/arel/engines/sql/relations/table.rb

@@ -82,6 +82,15 @@ def reset
       @columns = nil
       @attributes = Header.new([])
     end
+
+    private
+    def matching_attributes
+      @matching_attributes ||= Hash[attributes.map { |a| [a.root, true] }]
+    end
+
+    def has_attribute?(attribute)
+      matching_attributes.key? attribute.root
+    end
   end
 end