adding a DISTINCT node

3 files changed, 21 insertions, 7 deletions

diff --git a/lib/arel/nodes/select_core.rb b/lib/arel/nodes/select_core.rb
index 7f577e0a05..bee0a5930c 100644
--- a/lib/arel/nodes/select_core.rb
+++ b/lib/arel/nodes/select_core.rb
@@ -2,15 +2,18 @@ module Arel
   module Nodes
     class SelectCore < Arel::Nodes::Node
       attr_accessor :top, :projections, :wheres, :groups
-      attr_accessor :having, :source
+      attr_accessor :having, :source, :set_quantifier
 
       def initialize
-        @source      = JoinSource.new nil
-        @top         = nil
-        @projections = []
-        @wheres      = []
-        @groups      = []
-        @having      = nil
+        @source         = JoinSource.new nil
+        @top            = nil
+
+        # http://savage.net.au/SQL/sql-92.bnf.html#set%20quantifier
+        @set_quantifier = nil
+        @projections    = []
+        @wheres         = []
+        @groups         = []
+        @having         = nil
       end
 
       def from
diff --git a/lib/arel/nodes/unary.rb b/lib/arel/nodes/unary.rb
index 1c834913fa..e6e40e6b13 100644
--- a/lib/arel/nodes/unary.rb
+++ b/lib/arel/nodes/unary.rb
@@ -23,5 +23,11 @@ module Arel
     }.each do |name|
       const_set(name, Class.new(Unary))
     end
+
+    class Distinct < Unary
+      def initialize expr = nil
+        super
+      end
+    end
   end
 end
diff --git a/lib/arel/visitors/to_sql.rb b/lib/arel/visitors/to_sql.rb
index 061e46a436..6aba31d94d 100644
--- a/lib/arel/visitors/to_sql.rb
+++ b/lib/arel/visitors/to_sql.rb
@@ -125,6 +125,7 @@ key on UpdateManager using UpdateManager#key=
         [
           "SELECT",
           (visit(o.top) if o.top),
+          (visit(o.set_quantifier) if o.set_quantifier),
           "#{o.projections.map { |x| visit x }.join ', '}",
           visit(o.source),
           ("WHERE #{o.wheres.map { |x| visit x }.join ' AND ' }" unless o.wheres.empty?),
@@ -137,6 +138,10 @@ key on UpdateManager using UpdateManager#key=
         visit o.expr
       end
 
+      def visit_Arel_Nodes_Distinct o
+        'DISTINCT'
+      end
+
       def visit_Arel_Nodes_With o
         "WITH #{o.children.map { |x| visit x }.join(', ')}"
       end