new isolation mode testing

data/src/entity_manager/system.py

@@ -4466,6 +4466,12 @@ def _lock_query_f(self, entity_class, options, query_buffer):
         lock = options.get("lock", False)
         if not lock: return
 
+        # verifies if the current engine operation is running under
+        # a serializable transaction isolation mode, if that's the
+        # case there's no need for lock (isolation is enought)
+        is_serializable = self.engine._is_serializable()
+        if is_serializable: return
+
         # checks if the current engine allows (contains support)
         # for the for update part of the query
         allow_for_update = self.engine._allow_for_update()

data/src/entity_mysql/system.py

@@ -687,6 +687,10 @@ def _encode_query(self, query):
     def _resolve_operator(self, operator):
         return operator
 
+    def _is_serializable(self):
+        connection = self.entity_manager.get_connection()
+        return connection._isolation == "serializable"
+
     def _escape_slash(self):
         return True
 
@@ -699,9 +703,6 @@ def _allow_alter_drop(self):
     def _allow_for_update(self):
         return True
 
-    def _allow_serializable(self):
-        return False
-
 class MysqlConnection(object):
     """
     Class representing an abstraction on top of

data/src/entity_pgsql/system.py

@@ -159,6 +159,7 @@ def connect(self, connection, parameters = {}):
         connection._user = user
         connection._host = host
         connection._database = database
+        connection._isolation = isolation
         connection._show_sql = show_sql
         connection.open()
         self._execute_query_t(
@@ -598,6 +599,10 @@ def _has_table_definition_result(self, table_name, cursor):
     def _resolve_operator(self, operator):
         return OPERATORS_MAP.get(operator, operator)
 
+    def _is_serializable(self):
+        connection = self.entity_manager.get_connection()
+        return connection._isolation == "serializable"
+
     def _escape_slash(self):
         return False
 
@@ -615,8 +620,5 @@ def _allow_for_update(self):
         # this is considered a major drawback towards pgsql usage
         return False
 
-    def _allow_serializable(self):
-        return True
-
 class IntegrityError(RuntimeError):
     pass

data/src/entity_sqlite/system.py

@@ -482,6 +482,9 @@ def _get_temporary(self):
     def _resolve_operator(self, operator):
         return operator
 
+    def _is_serializable(self):
+        return False
+
     def _escape_slash(self):
         return False
 
@@ -494,9 +497,6 @@ def _allow_alter_drop(self):
     def _allow_for_update(self):
         return False
 
-    def _allow_serializable(self):
-        return False
-
 class SqliteConnection(object):
     """
     Class representing an abstraction on top of