dealing with limits and offsets

1 files changed, 23 insertions, 1 deletions

diff --git a/lib/arel/visitors/oracle.rb b/lib/arel/visitors/oracle.rb
index afea683080..c3af68cc36 100644
--- a/lib/arel/visitors/oracle.rb
+++ b/lib/arel/visitors/oracle.rb
@@ -1,8 +1,10 @@
 module Arel
   module Visitors
     class Oracle < Arel::Visitors::ToSql
+      private
+
       def visit_Arel_Nodes_SelectStatement o
-        if o.limit && o.orders.empty?
+        if o.limit && o.orders.empty? && !o.offset
           o.cores.last.wheres.push Nodes::LessThanOrEqual.new(
             Nodes::SqlLiteral.new('ROWNUM'), o.limit
           )
@@ -10,6 +12,22 @@ module Arel
           return super
         end
 
+        if o.limit && o.offset
+          limit = o.limit.to_i
+          offset = o.offset
+          o.limit = nil
+          o.offset = nil
+          sql = super
+          return <<-eosql
+              SELECT * FROM (
+                SELECT raw_sql_.*, rownum raw_rnum_
+                FROM (#{sql}) raw_sql_
+                WHERE rownum <= #{offset.value.to_i + limit}
+              )
+              WHERE #{visit offset}
+          eosql
+        end
+
         if o.limit && !o.orders.empty?
           limit = o.limit
           o.limit = nil
@@ -18,6 +36,10 @@ module Arel
 
         super
       end
+
+      def visit_Arel_Nodes_Offset o
+        "raw_rnum_ > #{visit o.value}"
+      end
     end
   end
 end