deserialize_db_from_string() loads the full serialized database
contents, which might contain forward references and cycles. That
caused IntegrityError because constraints were checked immediately.
Now, it loads data in a transaction with constraint checks deferred
until the end of the transaction.
Previously, this test could modify global state by changing
connection.settings_dict. This dict is a reference to the same dict as
django.db.connections.databases['default'], which is thus also changed.
The cleanup of this test would replace connection.settings_dic` with a
saved copy, which would leave the dict itself modified.
Additionally, create_test_db() would also modify these same dicts, as
well as settings.databases['default']['NAME'] by adding a "test_"
prefix, which is what can cause problems later.
This patch:
- makes a complete copy of the connection and work on that, to improve
isolation.
- calls destroy_test_db() to let that code clean up anything done by
create_test_db().
Thanks Josh Smeaton, Mariusz Felisiak, Sergey Fedoseev, Simon Charettes,
Adam Chainz/Johnson and Tim Graham for comments and reviews and Jamie
Cockburn for initial patch.
Mariusz Felisiak
Matthijs Kooijman
Jon Dufresne
Ville Skyttä
Simon Charette
Tim Graham
Matthew Wilkes
Mads Jensen
Shai Berger