Special limited delete handling in MSSQL

Refernce:
https://technet.microsoft.com/en-us/library/ms175486%28v=sql.105%29.aspx

lib/arel/visitors/mssql.rb

@@ -66,6 +66,23 @@ module Arel
         end
       end
 
+      def visit_Arel_Nodes_DeleteStatement o, collector
+        collector << 'DELETE '
+        if o.limit
+          collector << 'TOP ('
+          visit o.limit.expr, collector
+          collector << ') '
+        end
+        collector << 'FROM '
+        collector = visit o.relation, collector
+        if o.wheres.any?
+          collector << ' WHERE '
+          inject_join o.wheres, collector, AND
+        else
+          collector
+        end
+      end
+
       def determine_order_by orders, x
         if orders.any?
           orders

lib/arel/visitors/to_sql.rb

@@ -74,10 +74,10 @@ module Arel
       end
 
       def visit_Arel_Nodes_DeleteStatement o, collector
-        collector << "DELETE FROM "
+        collector << 'DELETE FROM '
         collector = visit o.relation, collector
         if o.wheres.any?
-          collector << " WHERE "
+          collector << ' WHERE '
           collector = inject_join o.wheres, collector, AND
         end
 

test/visitors/test_mssql.rb

@@ -45,6 +45,15 @@ module Arel
         connection.verify
       end
 
+      it 'should use TOP for limited deletes' do
+        stmt = Nodes::DeleteStatement.new
+        stmt.relation = @table
+        stmt.limit = Nodes::Limit.new(10)
+        sql = compile(stmt)
+
+        sql.must_be_like "DELETE TOP (10) FROM \"users\""
+      end
+
       it 'should go over query ORDER BY if .order()' do
         stmt = Nodes::SelectStatement.new
         stmt.limit = Nodes::Limit.new(10)