Commit abcf28a0 authored by valtron's avatar valtron Committed by Tim Graham
Browse files

Fixed #23474 -- Prevented migrating backwards from unapplying the wrong migrations.

parent 021f963e

django/db/migrations/executor.py

+9 −5
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@@ -36,11 +36,15 @@ class MigrationExecutor(object): 
            # If the migration is already applied, do backwards mode,

            # otherwise do forwards mode.

            elif target in applied:

                backwards_plan = self.loader.graph.backwards_plan(target)[:-1]

                # We only do this if the migration is not the most recent one

                # in its app - that is, another migration with the same app

                # label is in the backwards plan

                if any(node[0] == target[0] for node in backwards_plan):

                app_label = target[0]

                next_migration_prefix = str(int(target[1][:4]) + 1)

                try:

                    next_migration = self.loader.get_migration_by_prefix(app_label, next_migration_prefix)

                except KeyError:

                    # If `target` is the most recent one in its app, there is nothing to do.

                    pass

                else:

                    backwards_plan = self.loader.graph.backwards_plan(next_migration)

                    for migration in backwards_plan:

                        if migration in applied:

                            plan.append((self.loader.graph.nodes[migration], True))

docs/releases/1.7.1.txt

+3 −0
Original line number Diff line number Diff line
@@ -46,3 +46,6 @@ Bugfixes 


* Allowed migrations to work with ``app_label``\s that have the same last

  part (e.g. ``django.contrib.auth`` and ``vendor.auth``) (:ticket:`23483`).



* Fixed bug in migrations that could cause unexpected data loss when executing

  a backwards or no-op migration (:ticket:`23474`).

tests/migrations/test_executor.py

+38 −0
Original line number Diff line number Diff line
@@ -231,3 +231,41 @@ class ExecutorTests(MigrationTestBase): 
        executor.migrate([("migrations", None)])

        self.assertTableNotExists("migrations_author")

        self.assertTableNotExists("migrations_tribble")



    @override_settings(

        MIGRATION_MODULES={

          "migrations": "migrations.test_migrations_backwards_deps_1",

          "migrations2": "migrations2.test_migrations_backwards_deps_2",

        },

    )

    def test_backwards_deps(self):

        """

        #23474 - Migrating backwards shouldn't cause the wrong migrations to be

        unapplied.



        Migration dependencies (x -> y === y depends on x):

        m.0001 -+-> m.0002

                +-> m2.0001



        1) Migrate m2 to 0001, causing { m.0001, m2.0002 } to be applied.

        2) Migrate m to 0001. m.0001 has already been applied, so this should

           be a noop.

        """

        executor = MigrationExecutor(connection)

        executor.migrate([("migrations2", "0001_initial")])

        try:

            self.assertTableExists("migrations2_example")

            # Rebuild the graph to reflect the new DB state

            executor.loader.build_graph()

            self.assertEqual(

                executor.migration_plan([("migrations", "0001_initial")]),

                [],

            )

            executor.migrate([("migrations", "0001_initial")])

            self.assertTableExists("migrations2_example")

        finally:

            # And migrate back to clean up the database

            executor.loader.build_graph()

            executor.migrate([("migrations", None)])

            self.assertTableNotExists("migrations_author")

            self.assertTableNotExists("migrations_tribble")

tests/migrations/test_migrations_backwards_deps_1/0001_initial.py

0 → 100644
+8 −0
Original line number Diff line number Diff line 
# -*- coding: utf-8 -*-

from __future__ import unicode_literals



from django.db import migrations, models





class Migration(migrations.Migration):

    operations = []

tests/migrations/test_migrations_backwards_deps_1/0002_second.py

0 → 100644
+9 −0
Original line number Diff line number Diff line 
# -*- coding: utf-8 -*-

from __future__ import unicode_literals



from django.db import migrations, models





class Migration(migrations.Migration):

    dependencies = [('migrations', '0001_initial')]

    operations = []