Operations documentation

core/operations.py

@@ -22,13 +22,27 @@
 #
 #
 
+"""
+    This page is useful for custom migration tricks.
+    Sometimes, when you need to have a migration hack and you think it can be
+    useful again, put it there, we never know if we might need the hack again.
+"""
+
 from django.db import connection, migrations
 
 
 class PsqlRunOnly(migrations.RunSQL):
     """
-        Usefull for migrations with specific postgresql commands
-        Avoid breaking tests and local dev environnment
+        This is an SQL runner that will launch the given command only if
+        the used DBMS is PostgreSQL.
+        It may be useful to run Postgres' specific SQL, or to take actions
+        that would be non-senses with backends other than Postgre, such 
+        as disabling particular constraints that would prevent the migration
+        to run successfully.
+
+        See `club/migrations/0010_auto_20170912_2028.py` as an example.
+        Some explanations can be found here too: 
+        https://stackoverflow.com/questions/28429933/django-migrations-using-runpython-to-commit-changes
     """
 
     def _run_sql(self, schema_editor, sqls):