5 files changed, 52 insertions, 10 deletions
diff --git a/lib/arel/algebra/predicates.rb b/lib/arel/algebra/predicates.rb
index e98e152dbd..1b9667ac13 100644
--- a/lib/arel/algebra/predicates.rb
+++ b/lib/arel/algebra/predicates.rb
@@ -109,7 +109,7 @@ module Arel
 
     class Equality < Binary
       def ==(other)
-        Equality === other and
+        self.class === other and
           ((operand1 == other.operand1 and operand2 == other.operand2) or
            (operand1 == other.operand2 and operand2 == other.operand1))
       end
@@ -119,13 +119,7 @@ module Arel
       end
     end
 
-    class Inequality  < Binary
-      def ==(other)
-        Equality === other and
-          ((operand1 == other.operand1 and operand2 == other.operand2) or
-           (operand1 == other.operand2 and operand2 == other.operand1))
-      end
-
+    class Inequality < Equality
       def complement
         Equality.new(operand1, operand2)
       end
diff --git a/lib/arel/engines/memory/predicates.rb b/lib/arel/engines/memory/predicates.rb
index cca6739424..e36afa38c2 100644
--- a/lib/arel/engines/memory/predicates.rb
+++ b/lib/arel/engines/memory/predicates.rb
@@ -52,7 +52,7 @@ module Arel
       def operator; :== end
     end
 
-    class Inequality < Binary
+    class Inequality < Equality
       def eval(row)
         operand1.eval(row) != operand2.eval(row)
       end
diff --git a/lib/arel/engines/sql/predicates.rb b/lib/arel/engines/sql/predicates.rb
index 93d2a2f619..21d8f840c9 100644
--- a/lib/arel/engines/sql/predicates.rb
+++ b/lib/arel/engines/sql/predicates.rb
@@ -52,7 +52,7 @@ module Arel
       end
     end
 
-    class Inequality < Binary
+    class Inequality < Equality
       def predicate_sql
         operand2.inequality_predicate_sql
       end
diff --git a/spec/algebra/unit/predicates/inequality_spec.rb b/spec/algebra/unit/predicates/inequality_spec.rb
new file mode 100644
index 0000000000..557494e2cd
--- /dev/null
+++ b/spec/algebra/unit/predicates/inequality_spec.rb
@@ -0,0 +1,26 @@
+require 'spec_helper'
+
+module Arel
+  module Predicates
+    describe Inequality do
+      before do
+        relation1 = Arel::Table.new(:users)
+        relation2 = Arel::Table.new(:photos)
+        left      = relation1[:id]
+        right     = relation2[:user_id]
+        @a        = Inequality.new(left, right)
+        @b        = Inequality.new(right, left)
+      end
+
+      describe '==' do
+        it "is equal to itself" do
+          @a.should == @a
+        end
+
+        it "should not care abount children order" do
+          @a.should == @b
+        end
+      end
+    end
+  end
+end
diff --git a/spec/algebra/unit/predicates/predicate_spec.rb b/spec/algebra/unit/predicates/predicate_spec.rb
new file mode 100644
index 0000000000..6acc047cbb
--- /dev/null
+++ b/spec/algebra/unit/predicates/predicate_spec.rb
@@ -0,0 +1,22 @@
+require 'spec_helper'
+
+module Arel
+  module Predicates
+    describe Polyadic do
+      before do
+        @relation1 = Arel::Table.new(:users)
+        @relation2 = Arel::Table.new(:photos)
+        @a = @relation1[:id]
+        @b = @relation2[:user_id]
+      end
+
+      describe '==' do
+        left = Polyadic.new @a, @b
+        right = Polyadic.new @b, @a
+
+        left.should != right
+        left.should == right
+      end
+    end
+  end
+end