Opened 4 months ago

Last modified 4 months ago

#29052 new Bug

test database setup can truncate non-test database if two database aliases point to the same database

Reported by: Muse Owned by: nobody
Component: Testing framework Version: 2.0
Severity: Normal Keywords:
Cc: Triage Stage: Accepted
Has patch: no Needs documentation: no
Needs tests: no Patch needs improvement: no
Easy pickings: no UI/UX: no



When your database config look like following code, reader is the same as default.

"default" is the data source database.

    'default': {
        'ENGINE': 'django.db.backends.mysql',
        'NAME': 'test',
        'USER': 'root',
        'PASSWORD': 'xxxx.',
        'HOST': "",
        'PORT': '',

        "TEST": {
            "COLLATION": "utf8_general_ci",
            "CHARSET": "utf8",

    'reader': {
        'ENGINE': 'django.db.backends.mysql',
        'NAME': 'test',
        'USER': 'root',
        'PASSWORD': 'xxxx.',
        'HOST': "",
        'PORT': '',

        "TEST": {
            "COLLATION": "utf8_general_ci",
            "CHARSET": "utf8",

When I run ./ test, this's a chance that db test will be truncated, all data will be removed.
My project run under 1.11.2, but I tested on 2.0.1, problem remained.


I following the code, when test database created, there's a method at django/test/ was called by unittest.

    def _fixture_teardown(self):
        # Allow TRUNCATE ... CASCADE and don't emit the post_migrate signal
        # when flushing only a subset of the apps
        for db_name in self._databases_names(include_mirrors=False):
            # Flush the database
            inhibit_post_migrate = (
                self.available_apps is not None or
                (   # Inhibit the post_migrate signal when using serialized
                    # rollback to avoid trying to recreate the serialized data.
                    self.serialized_rollback and
                    hasattr(connections[db_name], '_test_serialized_contents')
            call_command('flush', verbosity=0, interactive=False,
                         database=db_name, reset_sequences=False,
                         allow_cascade=self.available_apps is not None,

Calling command flush, there's my database murderer. When calling flush, they using db test not using test_test.

I kept tracing, when testing framework start to initialize environment, there's a function "setup_databases"(django/test/ called, it used to create test database.

def setup_databases(verbosity, interactive, keepdb=False, debug_sql=False, parallel=0, **kwargs):
    Create the test databases.
    test_databases, mirrored_aliases = get_unique_databases_and_mirrors()

    old_names = []

    for signature, (db_name, aliases) in test_databases.items():
        first_alias = None   
        for alias in aliases:
            connection = connections[alias]
            old_names.append((connection, db_name, first_alias is None))

            # Actually create the database for the first connection
            if first_alias is None:
                first_alias = alias
                    autoclobber=not interactive,
                    serialize=connection.settings_dict.get('TEST', {}).get('SERIALIZE', True),
                if parallel > 1:
                    for index in range(parallel):
                            number=index + 1,
            # Configure all other connections as mirrors of the first one

At my case, aliases looks like {"reader", "default"} or {"default", "reader"}.

When default was the first one, create_test_db made connections.get("default") point to test_test.

On the contrary, connections.get("reader") point to test_test. But , connections.get("default") still point to test.

When choosing which database to flush, if just one database. Just using default.

    def _databases_names(cls, include_mirrors=True):
        # If the test case has a multi_db=True flag, act on all databases,
        # including mirrors or not. Otherwise, just on the default DB.
        if getattr(cls, 'multi_db', False):
            return [
                alias for alias in connections
                if include_mirrors or not connections[alias].settings_dict['TEST']['MIRROR']
            return [DEFAULT_DB_ALIAS]

But default still point to test, not test_test, so, all data gone.

Change History (1)

comment:1 Changed 4 months ago by Tim Graham

Summary: running test command will truncate the data source database at some conditiontest database setup can truncate non-test database if two database aliases point to the same database
Triage Stage: UnreviewedAccepted

I haven't reproduced this, but the report makes sense.

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