diff --git a/gluon/dal.py b/gluon/dal.py
index e36ee7ba..c4529b44 100644
--- a/gluon/dal.py
+++ b/gluon/dal.py
@@ -2549,6 +2549,9 @@ class PostgreSQLAdapter(BaseAdapter):
         'geography': 'GEOGRAPHY',
         'big-id': 'BIGSERIAL PRIMARY KEY',
         'big-reference': 'BIGINT REFERENCES %(foreign_key)s ON DELETE %(on_delete_action)s',
+        'reference FK': ', CONSTRAINT FK_%(constraint_name)s FOREIGN KEY (%(field_name)s) REFERENCES %(foreign_key)s ON DELETE %(on_delete_action)s',
+        'reference TFK': ' CONSTRAINT FK_%(foreign_table)s_PK FOREIGN KEY (%(field_name)s) REFERENCES %(foreign_table)s (%(foreign_key)s) ON DELETE %(on_delete_action)s',
+
         }
 
     def varquote(self,name):
diff --git a/gluon/globals.py b/gluon/globals.py
index f4f0eb71..940d7f3e 100644
--- a/gluon/globals.py
+++ b/gluon/globals.py
@@ -546,6 +546,9 @@ class Session(Storage):
 
         # else the session goes in db
         elif response.session_storage_type == 'db':
+            # verify that session_id exists
+            if not response.session_id:
+                return
 
             # verify if tablename was set or used in connect
             if response.session_table_name and tablename == 'web2py_session':
diff --git a/gluon/tools.py b/gluon/tools.py
index b8e9a360..57486531 100644
--- a/gluon/tools.py
+++ b/gluon/tools.py
@@ -1450,7 +1450,7 @@ class Auth(object):
         """
         tables = [table for table in tables]
         for table in tables:
-            if 'modified_on' in table.fields() and not current_record in table.fields():
+            if '_id' in table.fields() and 'modified_on' in table.fields() and not current_record in table.fields():
                 table._enable_record_versioning(
                     archive_db=archive_db,
                     archive_name=archive_names,