adding more oracle hacks

1 files changed, 19 insertions, 0 deletions

diff --git a/lib/arel/visitors/oracle.rb b/lib/arel/visitors/oracle.rb
index c3af68cc36..46a3ad4c78 100644
--- a/lib/arel/visitors/oracle.rb
+++ b/lib/arel/visitors/oracle.rb
@@ -4,6 +4,8 @@ module Arel
       private
 
       def visit_Arel_Nodes_SelectStatement o
+        order_hacks(o)
+
         if o.limit && o.orders.empty? && !o.offset
           o.cores.last.wheres.push Nodes::LessThanOrEqual.new(
             Nodes::SqlLiteral.new('ROWNUM'), o.limit
@@ -40,6 +42,23 @@ module Arel
       def visit_Arel_Nodes_Offset o
         "raw_rnum_ > #{visit o.value}"
       end
+
+      ###
+      # Hacks for the order clauses specific to Oracle
+      def order_hacks o
+        return if o.orders.empty?
+        return unless o.cores.any? do |core|
+          core.projections.any? do |projection|
+            /DISTINCT.*FIRST_VALUE/ === projection
+          end
+        end
+        orders = o.orders
+        o.orders = []
+        orders.each_with_index do |order, i|
+          o.orders <<
+            Nodes::SqlLiteral.new("alias_#{i}__ #{'DESC' if /\bdesc$/i === order}")
+        end
+      end
     end
   end
 end