4 files changed, 95 insertions, 1 deletions
diff --git a/lib/arel/nodes/function.rb b/lib/arel/nodes/function.rb
index b6f6644678..5f6056a6b6 100644
--- a/lib/arel/nodes/function.rb
+++ b/lib/arel/nodes/function.rb
@@ -3,6 +3,7 @@ module Arel
     class Function < Arel::Nodes::Node
       include Arel::Expression
       include Arel::Predications
+      include Arel::WindowPredications
       attr_accessor :expressions, :alias, :distinct
 
       def initialize expr, aliaz = nil
diff --git a/lib/arel/nodes/over.rb b/lib/arel/nodes/over.rb
new file mode 100644
index 0000000000..727ccd2dc7
--- /dev/null
+++ b/lib/arel/nodes/over.rb
@@ -0,0 +1,13 @@
+module Arel
+  module Nodes
+
+    class Over < Binary
+      def initialize(left, right = nil)
+        super(left, right)
+      end
+
+      def operator; 'OVER' end
+    end
+
+  end
+end
+\ No newline at end of file
diff --git a/lib/arel/nodes/select_core.rb b/lib/arel/nodes/select_core.rb
index bee0a5930c..9b8c4a2a1f 100644
--- a/lib/arel/nodes/select_core.rb
+++ b/lib/arel/nodes/select_core.rb
@@ -1,7 +1,7 @@
 module Arel
   module Nodes
     class SelectCore < Arel::Nodes::Node
-      attr_accessor :top, :projections, :wheres, :groups
+      attr_accessor :top, :projections, :wheres, :groups, :windows
       attr_accessor :having, :source, :set_quantifier
 
       def initialize
@@ -14,6 +14,7 @@ module Arel
         @wheres         = []
         @groups         = []
         @having         = nil
+        @windows        = []
       end
 
       def from
@@ -34,6 +35,7 @@ module Arel
         @wheres      = @wheres.clone
         @groups      = @groups.clone
         @having      = @having.clone if @having
+        @windows     = @windows.clone
       end
     end
   end
diff --git a/lib/arel/nodes/window.rb b/lib/arel/nodes/window.rb
new file mode 100644
index 0000000000..b54eb7fe64
--- /dev/null
+++ b/lib/arel/nodes/window.rb
@@ -0,0 +1,78 @@
+module Arel
+  module Nodes
+    class Window < Arel::Nodes::Node
+      include Arel::Expression
+      attr_accessor :orders, :framing
+
+      def initialize
+        @orders = []
+      end
+
+      def order *expr
+        # FIXME: We SHOULD NOT be converting these to SqlLiteral automatically
+        @orders.concat expr.map { |x|
+          String === x || Symbol === x ? Nodes::SqlLiteral.new(x.to_s) : x
+        }
+        self
+      end
+
+      def frame(expr)
+        raise ArgumentError, "Window frame cannot be set more than once" if @frame
+        @framing = expr
+      end
+
+      def rows(expr = nil)
+        frame(Rows.new(expr))
+      end
+
+      def range(expr = nil)
+        frame(Range.new(expr))
+      end
+
+      def initialize_copy other
+        super
+        @orders = @orders.map { |x| x.clone }
+      end
+    end
+
+    class NamedWindow < Window
+      attr_accessor :name
+
+      def initialize name
+        super()
+        @name = name
+      end
+
+      def initialize_copy other
+        super
+        @name = other.name.clone
+      end
+    end
+
+    class Rows < Unary
+      def initialize(expr = nil)
+        super(expr)
+      end
+    end
+
+    class Range < Unary
+      def initialize(expr = nil)
+        super(expr)
+      end
+    end
+
+    class CurrentRow < Arel::Nodes::Node; end
+
+    class Preceding < Unary
+      def initialize(expr = nil)
+        super(expr)
+      end
+    end
+
+    class Following < Unary
+      def initialize(expr = nil)
+        super(expr)
+      end
+    end
+  end
+end
+\ No newline at end of file