Add support for a NOT predicate

4 files changed, 15 insertions, 0 deletions

diff --git a/lib/arel/algebra/attributes/attribute.rb b/lib/arel/algebra/attributes/attribute.rb
index 03cf44a552..b372be5e1d 100644
--- a/lib/arel/algebra/attributes/attribute.rb
+++ b/lib/arel/algebra/attributes/attribute.rb
@@ -86,6 +86,10 @@ module Arel
         Predicates::Equality.new(self, other)
       end
 
+      def not(other)
+        Predicates::Not.new(self, other)
+      end
+
       def lt(other)
         Predicates::LessThan.new(self, other)
       end
diff --git a/lib/arel/algebra/predicates.rb b/lib/arel/algebra/predicates.rb
index 8a0b41fa18..700cd6afaa 100644
--- a/lib/arel/algebra/predicates.rb
+++ b/lib/arel/algebra/predicates.rb
@@ -33,6 +33,7 @@ module Arel
       end
     end
 
+    class Not                   < Binary; end
     class GreaterThanOrEqualTo  < Binary; end
     class GreaterThan           < Binary; end
     class LessThanOrEqualTo     < Binary; end
diff --git a/lib/arel/engines/memory/predicates.rb b/lib/arel/engines/memory/predicates.rb
index dd2559c70f..f87bf68357 100644
--- a/lib/arel/engines/memory/predicates.rb
+++ b/lib/arel/engines/memory/predicates.rb
@@ -10,6 +10,12 @@ module Arel
       def operator; :== end
     end
 
+    class Not < Binary
+      def eval(row)
+        operand1.eval(row) != operand2.eval(row)
+      end
+    end
+
     class GreaterThanOrEqualTo < Binary
       def operator; :>= end
     end
diff --git a/lib/arel/engines/sql/predicates.rb b/lib/arel/engines/sql/predicates.rb
index e563a9ba3e..3756231a46 100644
--- a/lib/arel/engines/sql/predicates.rb
+++ b/lib/arel/engines/sql/predicates.rb
@@ -26,6 +26,10 @@ module Arel
       end
     end
 
+    class Not < Binary
+      def predicate_sql; '!=' end
+    end
+
     class GreaterThanOrEqualTo < Binary
       def predicate_sql; '>=' end
     end