diff --git a/activerecord/lib/active_record/associations/has_and_belongs_to_many_association.rb b/activerecord/lib/active_record/associations/has_and_belongs_to_many_association.rb
index 1c237eda33346bdf6defe65928bd23044eeb3908..a4194defc24e19528950edefb36066d7d1dec93e 100644
--- a/activerecord/lib/active_record/associations/has_and_belongs_to_many_association.rb
+++ b/activerecord/lib/active_record/associations/has_and_belongs_to_many_association.rb
@@ -83,7 +83,8 @@ def finder_options
           super.merge(
             :joins    => construct_joins,
             :readonly => ambiguous_select?(@reflection.options[:select]),
-            :select   => @reflection.options[:select] || Arel.star
+            :select   => @reflection.options[:select] ||
+              Arel.sql("#{@reflection.quoted_table_name}.*, #{@owner.connection.quote_table_name @reflection.options[:join_table]}.*")
           )
         end
 
diff --git a/activerecord/lib/active_record/relation/finder_methods.rb b/activerecord/lib/active_record/relation/finder_methods.rb
index 13f55319a77bf4d4c5dab383af9b934b5e33e190..8bbc47ab75063d75b81f2536beeac62e4230dcb8 100644
--- a/activerecord/lib/active_record/relation/finder_methods.rb
+++ b/activerecord/lib/active_record/relation/finder_methods.rb
@@ -171,7 +171,7 @@ def all(*args)
     def exists?(id = nil)
       id = id.id if ActiveRecord::Base === id
 
-      relation = select(table[primary_key]).limit(1)
+      relation = select("1").limit(1)
 
       case id
       when Array, Hash