Break Ordering into Ascending/Descending nodes, allow reversal

9 files changed, 59 insertions, 22 deletions

diff --git a/lib/arel/nodes.rb b/lib/arel/nodes.rb
index 9576930a54..9edf3a9a95 100644
--- a/lib/arel/nodes.rb
+++ b/lib/arel/nodes.rb
@@ -11,6 +11,8 @@ require 'arel/nodes/terminal'
 
 # unary
 require 'arel/nodes/unary'
+require 'arel/nodes/ascending'
+require 'arel/nodes/descending'
 require 'arel/nodes/unqualified_column'
 require 'arel/nodes/with'
 
@@ -19,7 +21,6 @@ require 'arel/nodes/binary'
 require 'arel/nodes/equality'
 require 'arel/nodes/in' # Why is this subclassed from equality?
 require 'arel/nodes/join_source'
-require 'arel/nodes/ordering'
 require 'arel/nodes/delete_statement'
 require 'arel/nodes/table_alias'
 require 'arel/nodes/infix_operation'
diff --git a/lib/arel/nodes/ascending.rb b/lib/arel/nodes/ascending.rb
new file mode 100644
index 0000000000..bca00a8339
--- /dev/null
+++ b/lib/arel/nodes/ascending.rb
@@ -0,0 +1,23 @@
+module Arel
+  module Nodes
+    class Ascending < Ordering
+
+      def reverse
+        Descending.new(expr)
+      end
+
+      def direction
+        :asc
+      end
+
+      def ascending?
+        true
+      end
+
+      def descending?
+        false
+      end
+
+    end
+  end
+end
diff --git a/lib/arel/nodes/descending.rb b/lib/arel/nodes/descending.rb
new file mode 100644
index 0000000000..d886bdcb5f
--- /dev/null
+++ b/lib/arel/nodes/descending.rb
@@ -0,0 +1,23 @@
+module Arel
+  module Nodes
+    class Descending < Ordering
+
+      def reverse
+        Ascending.new(expr)
+      end
+
+      def direction
+        :desc
+      end
+
+      def ascending?
+        false
+      end
+
+      def descending?
+        true
+      end
+
+    end
+  end
+end
diff --git a/lib/arel/nodes/ordering.rb b/lib/arel/nodes/ordering.rb
index 0a3621cf54..efb4d18ae4 100644
--- a/lib/arel/nodes/ordering.rb
+++ b/lib/arel/nodes/ordering.rb
@@ -1,20 +1,6 @@
 module Arel
   module Nodes
-    class Ordering < Arel::Nodes::Binary
-      alias :expr :left
-      alias :direction :right
-
-      def initialize expr, direction = :asc
-        super
-      end
-
-      def ascending?
-        direction == :asc
-      end
-
-      def descending?
-        direction == :desc
-      end
+    class Ordering < Unary
     end
   end
 end
diff --git a/lib/arel/nodes/unary.rb b/lib/arel/nodes/unary.rb
index 5c4add4792..4688fff623 100644
--- a/lib/arel/nodes/unary.rb
+++ b/lib/arel/nodes/unary.rb
@@ -18,6 +18,7 @@ module Arel
       Not
       Offset
       On
+      Ordering
       Top
       Lock
       DistinctOn
diff --git a/lib/arel/order_predications.rb b/lib/arel/order_predications.rb
index af163c9454..153fcffb41 100644
--- a/lib/arel/order_predications.rb
+++ b/lib/arel/order_predications.rb
@@ -2,11 +2,11 @@ module Arel
   module OrderPredications
 
     def asc
-      Nodes::Ordering.new self, :asc
+      Nodes::Ascending.new self
     end
 
     def desc
-      Nodes::Ordering.new self, :desc
+      Nodes::Descending.new self
     end
 
   end
diff --git a/lib/arel/visitors/depth_first.rb b/lib/arel/visitors/depth_first.rb
index 914b2d1999..6f9385de1b 100644
--- a/lib/arel/visitors/depth_first.rb
+++ b/lib/arel/visitors/depth_first.rb
@@ -22,6 +22,7 @@ module Arel
       alias :visit_Arel_Nodes_Not               :unary
       alias :visit_Arel_Nodes_Offset            :unary
       alias :visit_Arel_Nodes_On                :unary
+      alias :visit_Arel_Nodes_Ordering          :unary
       alias :visit_Arel_Nodes_Top               :unary
       alias :visit_Arel_Nodes_UnqualifiedColumn :unary
 
@@ -75,7 +76,6 @@ module Arel
       alias :visit_Arel_Nodes_NotEqual           :binary
       alias :visit_Arel_Nodes_NotIn              :binary
       alias :visit_Arel_Nodes_Or                 :binary
-      alias :visit_Arel_Nodes_Ordering           :binary
       alias :visit_Arel_Nodes_OuterJoin          :binary
       alias :visit_Arel_Nodes_TableAlias         :binary
       alias :visit_Arel_Nodes_Values             :binary
diff --git a/lib/arel/visitors/dot.rb b/lib/arel/visitors/dot.rb
index 92d05c7b67..8303279211 100644
--- a/lib/arel/visitors/dot.rb
+++ b/lib/arel/visitors/dot.rb
@@ -30,7 +30,6 @@ module Arel
       private
       def visit_Arel_Nodes_Ordering o
         visit_edge o, "expr"
-        visit_edge o, "direction"
       end
 
       def visit_Arel_Nodes_TableAlias o
diff --git a/lib/arel/visitors/to_sql.rb b/lib/arel/visitors/to_sql.rb
index 29e965bef8..933edc15f2 100644
--- a/lib/arel/visitors/to_sql.rb
+++ b/lib/arel/visitors/to_sql.rb
@@ -203,8 +203,12 @@ key on UpdateManager using UpdateManager#key=
         "(#{visit o.expr})"
       end
 
-      def visit_Arel_Nodes_Ordering o
-        "#{visit o.expr} #{o.descending? ? 'DESC' : 'ASC'}"
+      def visit_Arel_Nodes_Ascending o
+        "#{visit o.expr} ASC"
+      end
+
+      def visit_Arel_Nodes_Descending o
+        "#{visit o.expr} DESC"
       end
 
       def visit_Arel_Nodes_Group o