1 files changed, 10 insertions, 1 deletions
diff --git a/activerecord/lib/active_record/connection_adapters/abstract/schema_definitions.rb b/activerecord/lib/active_record/connection_adapters/abstract/schema_definitions.rb
index 2e47e68754..785cfd9dbc 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract/schema_definitions.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract/schema_definitions.rb
@@ -35,7 +35,7 @@ module ActiveRecord
       end
 
       def primary_key
-        options[:primary_key]
+        options[:primary_key] || default_primary_key
       end
 
       def on_delete
@@ -45,6 +45,15 @@ module ActiveRecord
       def on_update
         options[:on_update]
       end
+
+      def custom_primary_key?
+        options[:primary_key] != default_primary_key
+      end
+
+      private
+      def default_primary_key
+        "id"
+      end
     end
 
     # Represents the schema of an SQL table in an abstract way. This class