Raise error on unknown primary key.

If we don't have a primary key when we ask for it, it's better to fail
fast. Fixes GH #2307.

1 files changed, 3 insertions, 3 deletions

diff --git a/activerecord/lib/active_record/attribute_methods/read.rb b/activerecord/lib/active_record/attribute_methods/read.rb
index 4174e4da09..8566ecad14 100644
--- a/activerecord/lib/active_record/attribute_methods/read.rb
+++ b/activerecord/lib/active_record/attribute_methods/read.rb
@@ -40,7 +40,7 @@ module ActiveRecord
               define_read_method(attr_name, attr_name, columns_hash[attr_name])
             end
 
-            if attr_name == primary_key && attr_name != "id"
+            if primary_key? && attr_name == primary_key && attr_name != "id"
               define_read_method('id', attr_name, columns_hash[attr_name])
             end
           end
@@ -63,7 +63,7 @@ module ActiveRecord
             cast_code = column.type_cast_code('v')
             access_code = "(v=@attributes['#{attr_name}']) && #{cast_code}"
 
-            unless attr_name.to_s == self.primary_key.to_s
+            unless primary_key? && attr_name.to_s == primary_key.to_s
               access_code.insert(0, "missing_attribute('#{attr_name}', caller) unless @attributes.has_key?('#{attr_name}'); ")
             end
 
@@ -107,7 +107,7 @@ module ActiveRecord
 
       def _read_attribute(attr_name)
         attr_name = attr_name.to_s
-        attr_name = self.class.primary_key if attr_name == 'id'
+        attr_name = self.class.primary_key? && self.class.primary_key if attr_name == 'id'
         value = @attributes[attr_name]
         unless value.nil?
           if column = column_for_attribute(attr_name)