[Rails3] Account for symbols passed to :select option.

Author: metaskills

lib/arel/engines/sql/compilers/sqlserver_compiler.rb

@@ -50,7 +50,7 @@ def eager_limiting_select?
       end
 
       def single_distinct_select?
-        relation.select_clauses.size == 1 && relation.select_clauses.first.include?('DISTINCT')
+        relation.select_clauses.size == 1 && relation.select_clauses.first.to_s.include?('DISTINCT')
       end
 
       def all_select_clauses_aliased?