Merge commit 'rails/master'

Conflicts:
	activerecord/lib/active_record/calculations.rb
	activerecord/lib/active_record/connection_adapters/mysql_adapter.rb
	activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb

1 files changed, 7 insertions, 0 deletions

diff --git a/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb b/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb
index c533d4cdb6..fab70f34b9 100755
--- a/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb
@@ -56,6 +56,13 @@ module ActiveRecord
         false
       end
 
+      # Can this adapter determine the primary key for tables not attached
+      # to an ActiveRecord class, such as join tables?  Backend specific, as
+      # the abstract adapter always returns +false+.
+      def supports_primary_key?
+        false
+      end
+
       # Does this adapter support using DISTINCT within COUNT?  This is +true+
       # for all adapters except sqlite.
       def supports_count_distinct?