Add inital legacy migration code

legacy/legacy_migration.py

@@ -0,0 +1,36 @@
+from django.db import connection
+
+import legacy
+from parlamentares.models import NivelInstrucao
+
+
+mappings = (
+    (NivelInstrucao,
+        'cod_nivel_instrucao',
+     [('des_nivel_instrucao', 'nivel_instrucao')]),
+)
+
+
+def run_legacy_migration():
+
+    for model, pk, field_pairs in mappings:
+
+        # clear all model entries
+        model.objects.all().delete()
+        # resets id sequence
+        sql_reset_seq = 'ALTER SEQUENCE %s_id_seq RESTART WITH 1;' % model._meta.db_table
+        cursor = connection.cursor()
+        cursor.execute(sql_reset_seq)
+
+        legacy_model = getattr(legacy.models, model.__name__)
+        for old in legacy_model.objects.all().order_by(pk):
+            old_id = getattr(old, pk)
+            new = model()
+            while not new.id:
+                for old_field, new_field in field_pairs:
+                    setattr(new, new_field, getattr(old, old_field))
+                new.save()
+                assert new.id <= old_id, 'New id exceeds old one. Be sure your new table was just created!'
+                if new.id < old_id:
+                    new.delete()
+                    new = model()