# HG changeset patch
# User Thierry Florac <thierry.florac@onf.fr>
# Date 1435738580 -7200
# Node ID d775bab6f983e0892425668a0474873c2ef22c0c
# Parent  d114654e742314f101dbb725dbefeafd984130bc
Added DataLoader class to help data migration between databases

diff -r d114654e7423 -r d775bab6f983 src/pyams_alchemy/loader.py
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/pyams_alchemy/loader.py	Wed Jul 01 10:16:20 2015 +0200
@@ -0,0 +1,56 @@
+#
+# Copyright (c) 2008-2015 Thierry Florac <tflorac AT ulthar.net>
+# All Rights Reserved.
+#
+# This software is subject to the provisions of the Zope Public License,
+# Version 2.1 (ZPL).  A copy of the ZPL should accompany this distribution.
+# THIS SOFTWARE IS PROVIDED "AS IS" AND ANY AND ALL EXPRESS OR IMPLIED
+# WARRANTIES ARE DISCLAIMED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+# WARRANTIES OF TITLE, MERCHANTABILITY, AGAINST INFRINGEMENT, AND FITNESS
+# FOR A PARTICULAR PURPOSE.
+#
+
+__docformat__ = 'restructuredtext'
+
+
+# import standard library
+import logging
+logger = logging.getLogger('PyAMS (alchemy)')
+
+# import interfaces
+
+# import packages
+from pyams_alchemy.engine import get_user_session
+from sqlalchemy.orm.session import make_transient
+
+
+class DataLoader(object):
+    """SQLAlchemy data loader
+
+    This utility class is used to migrate entities from a given connection
+    to another one.
+    WARNING: actually, given entities must share the same schema name!!!
+    """
+
+    def __init__(self, source, target, entities):
+        """
+        Initialize data loader
+
+        :param source: name of registered source engine
+        :param target: name of registered target engine
+        :param entities: list of migrated entities
+        :return:
+        """
+        self.source_session = get_user_session(source)
+        self.target_session = get_user_session(target)
+        self.entities = entities
+
+    def run(self):
+        source = self.source_session
+        target = self.target_session
+        for entity in self.entities:
+            logger.info('Loading entity {0!r}'.format(entity))
+            for record in source.query(entity):
+                source.expunge(record)
+                make_transient(record)
+                target.add(record)