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Fixed #25833 -- Added support for non-atomic migrations. 

Added the Migration.atomic attribute which can be set to False
for non-atomic migrations.
This commit is contained in:
Pankrat 2016-01-30 21:46:28 +01:00 committed by Tim Graham
parent 0edb8a146f
commit f91a04621e
14 changed files with 181 additions and 16 deletions
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3
django/core/management/commands/sqlmigrate.py
View File

@ -51,6 +51,9 @@ class Command(BaseCommand):
migration_name, app_label))
targets = [(app_label, migration.name)]
# Show begin/end around output only for atomic migrations
self.output_transaction = migration.atomic
# Make a plan that represents just the requested migrations and show SQL
# for it
plan = [(executor.loader.graph.nodes[targets[0]], options['backwards'])]

7
django/db/backends/base/schema.py
View File

@ -69,17 +69,18 @@ class BaseDatabaseSchemaEditor(object):
sql_create_pk = "ALTER TABLE %(table)s ADD CONSTRAINT %(name)s PRIMARY KEY (%(columns)s)"
sql_delete_pk = "ALTER TABLE %(table)s DROP CONSTRAINT %(name)s"
def __init__(self, connection, collect_sql=False):
def __init__(self, connection, collect_sql=False, atomic=True):
self.connection = connection
self.collect_sql = collect_sql
if self.collect_sql:
self.collected_sql = []
self.atomic_migration = self.connection.features.can_rollback_ddl and atomic
# State-managing methods
def __enter__(self):
self.deferred_sql = []
if self.connection.features.can_rollback_ddl:
if self.atomic_migration:
self.atomic = atomic(self.connection.alias)
self.atomic.__enter__()
return self
@ -88,7 +89,7 @@ class BaseDatabaseSchemaEditor(object):
if exc_type is None:
for sql in self.deferred_sql:
self.execute(sql)
if self.connection.features.can_rollback_ddl:
if self.atomic_migration:
self.atomic.__exit__(exc_type, exc_value, traceback)
# Core utility functions

6
django/db/migrations/executor.py
View File

@ -170,7 +170,7 @@ class MigrationExecutor(object):
statements = []
state = None
for migration, backwards in plan:
with self.connection.schema_editor(collect_sql=True) as schema_editor:
with self.connection.schema_editor(collect_sql=True, atomic=migration.atomic) as schema_editor:
if state is None:
state = self.loader.project_state((migration.app_label, migration.name), at_end=False)
if not backwards:
@ -194,7 +194,7 @@ class MigrationExecutor(object):
fake = True
if not fake:
# Alright, do it normally
with self.connection.schema_editor() as schema_editor:
with self.connection.schema_editor(atomic=migration.atomic) as schema_editor:
state = migration.apply(state, schema_editor)
# For replacement migrations, record individual statuses
if migration.replaces:
@ -214,7 +214,7 @@ class MigrationExecutor(object):
if self.progress_callback:
self.progress_callback("unapply_start", migration, fake)
if not fake:
with self.connection.schema_editor() as schema_editor:
with self.connection.schema_editor(atomic=migration.atomic) as schema_editor:
state = migration.unapply(state, schema_editor)
# For replacement migrations, record individual statuses
if migration.replaces:

10
django/db/migrations/migration.py
View File

@ -48,6 +48,10 @@ class Migration(object):
# introspection. If False, never perform introspection.
initial = None
# Whether to wrap the whole migration in a transaction. Only has an effect
# on database backends which support transactional DDL.
atomic = True
def __init__(self, name, app_label):
self.name = name
self.app_label = app_label
@ -114,8 +118,10 @@ class Migration(object):
old_state = project_state.clone()
operation.state_forwards(self.app_label, project_state)
# Run the operation
if not schema_editor.connection.features.can_rollback_ddl and operation.atomic:
# We're forcing a transaction on a non-transactional-DDL backend
atomic_operation = operation.atomic or (self.atomic and operation.atomic is not False)
if not schema_editor.atomic_migration and atomic_operation:
# Force a transaction on a non-transactional-DDL backend or an
# atomic operation inside a non-atomic migration.
with atomic(schema_editor.connection.alias):
operation.database_forwards(self.app_label, schema_editor, old_state, project_state)
else:

4
django/db/migrations/operations/special.py
View File

@ -139,7 +139,7 @@ class RunPython(Operation):
reduces_to_sql = False
def __init__(self, code, reverse_code=None, atomic=True, hints=None, elidable=False):
def __init__(self, code, reverse_code=None, atomic=None, hints=None, elidable=False):
self.atomic = atomic
# Forwards code
if not callable(code):
@ -161,7 +161,7 @@ class RunPython(Operation):
}
if self.reverse_code is not None:
kwargs['reverse_code'] = self.reverse_code
if self.atomic is not True:
if self.atomic is not None:
kwargs['atomic'] = self.atomic
if self.hints:
kwargs['hints'] = self.hints

47
docs/howto/writing-migrations.txt
View File

@ -184,6 +184,53 @@ the respective field according to your needs.
migration is running. Objects created after the ``AddField`` and before
``RunPython`` will have their original ``uuid``’s overwritten.
.. _non-atomic-migrations:
Non-atomic migrations
~~~~~~~~~~~~~~~~~~~~~
.. versionadded:: 1.10
On databases that support DDL transactions (SQLite and PostgreSQL), migrations
will run inside a transaction by default. For use cases such as performing data
migrations on large tables, you may want to prevent a migration from running in
a transaction by setting the ``atomic`` attribute to ``False``::
from django.db import migrations
class Migration(migrations.Migration):
atomic = False
Within such a migration, all operations are run without a transaction. It's
possible to execute parts of the migration inside a transaction using
:func:`~django.db.transaction.atomic()` or by passing ``atomic=True`` to
``RunPython``.
Here's an example of a non-atomic data migration that updates a large table in
smaller batches::
import uuid
from django.db import migrations, transaction
def gen_uuid(apps, schema_editor):
MyModel = apps.get_model('myapp', 'MyModel')
while MyModel.objects.filter(uuid__isnull=True).exists():
with transaction.atomic():
for row in MyModel.objects.filter(uuid__isnull=True)[:1000]:
row.uuid = uuid.uuid4()
row.save()
class Migration(migrations.Migration):
atomic = False
operations = [
migrations.RunPython(gen_uuid),
]
The ``atomic`` attribute doesn't have an effect on databases that don't support
DDL transactions (e.g. MySQL, Oracle).
Controlling the order of migrations
===================================

20
docs/ref/migration-operations.txt
View File

@ -269,7 +269,7 @@ be removed (elided) when :ref:`squashing migrations <migration-squashing>`.
``RunPython``
-------------
.. class:: RunPython(code, reverse_code=None, atomic=True, hints=None, elidable=False)
.. class:: RunPython(code, reverse_code=None, atomic=None, hints=None, elidable=False)
Runs custom Python code in a historical context. ``code`` (and ``reverse_code``
if supplied) should be callable objects that accept two arguments; the first is
@ -354,16 +354,19 @@ the ``schema_editor`` provided on these backends; in this case, pass
On databases that do support DDL transactions (SQLite and PostgreSQL),
``RunPython`` operations do not have any transactions automatically added
besides the transactions created for each migration (the ``atomic`` parameter
has no effect on these databases). Thus, on PostgreSQL, for example, you should
avoid combining schema changes and ``RunPython`` operations in the same
migration or you may hit errors like ``OperationalError: cannot ALTER TABLE
"mytable" because it has pending trigger events``.
besides the transactions created for each migration. Thus, on PostgreSQL, for
example, you should avoid combining schema changes and ``RunPython`` operations
in the same migration or you may hit errors like ``OperationalError: cannot
ALTER TABLE "mytable" because it has pending trigger events``.
If you have a different database and aren't sure if it supports DDL
transactions, check the ``django.db.connection.features.can_rollback_ddl``
attribute.
If the ``RunPython`` operation is part of a :ref:`non-atomic migration
<non-atomic-migrations>`, the operation will only be executed in a transaction
if ``atomic=True`` is passed to the ``RunPython`` operation.
.. warning::
``RunPython`` does not magically alter the connection of the models for you;
@ -382,6 +385,11 @@ attribute.
The ``elidable`` argument was added.
.. versionchanged:: 1.10
The ``atomic`` argument default was changed to ``None``, indicating that
the atomicity is controlled by the ``atomic`` attribute of the migration.
``SeparateDatabaseAndState``
----------------------------

3
docs/releases/1.10.txt
View File

@ -258,6 +258,9 @@ Migrations
:class:`~django.db.migrations.operations.RunPython` operations to allow them
to be removed when squashing migrations.
* Added support for :ref:`non-atomic migrations <non-atomic-migrations>` by
setting the ``atomic`` attribute on a ``Migration``.
Models
~~~~~~

13
tests/migrations/test_commands.py
View File

@ -362,6 +362,19 @@ class MigrateTests(MigrationTestBase):
# Cleanup by unmigrating everything
call_command("migrate", "migrations", "zero", verbosity=0)
@override_settings(MIGRATION_MODULES={"migrations": "migrations.test_migrations_non_atomic"})
def test_sqlmigrate_for_non_atomic_migration(self):
"""
Transaction wrappers aren't shown for non-atomic migrations.
"""
out = six.StringIO()
call_command("sqlmigrate", "migrations", "0001", stdout=out)
output = out.getvalue().lower()
queries = [q.strip() for q in output.splitlines()]
if connection.ops.start_transaction_sql():
self.assertNotIn(connection.ops.start_transaction_sql().lower(), queries)
self.assertNotIn(connection.ops.end_transaction_sql().lower(), queries)
@override_settings(
INSTALLED_APPS=[
"migrations.migrations_test_apps.migrated_app",

27
tests/migrations/test_executor.py
View File

@ -100,6 +100,33 @@ class ExecutorTests(MigrationTestBase):
self.assertTableNotExists("migrations_author")
self.assertTableNotExists("migrations_book")
@override_settings(MIGRATION_MODULES={"migrations": "migrations.test_migrations_non_atomic"})
def test_non_atomic_migration(self):
"""
Applying a non-atomic migration works as expected.
"""
executor = MigrationExecutor(connection)
with self.assertRaisesMessage(RuntimeError, "Abort migration"):
executor.migrate([("migrations", "0001_initial")])
self.assertTableExists("migrations_publisher")
migrations_apps = executor.loader.project_state(("migrations", "0001_initial")).apps
Publisher = migrations_apps.get_model("migrations", "Publisher")
self.assertTrue(Publisher.objects.exists())
self.assertTableNotExists("migrations_book")
@override_settings(MIGRATION_MODULES={"migrations": "migrations.test_migrations_atomic_operation"})
def test_atomic_operation_in_non_atomic_migration(self):
"""
An atomic operation is properly rolled back inside a non-atomic
migration.
"""
executor = MigrationExecutor(connection)
with self.assertRaisesMessage(RuntimeError, "Abort migration"):
executor.migrate([("migrations", "0001_initial")])
migrations_apps = executor.loader.project_state(("migrations", "0001_initial")).apps
Editor = migrations_apps.get_model("migrations", "Editor")
self.assertFalse(Editor.objects.exists())
@override_settings(MIGRATION_MODULES={
"migrations": "migrations.test_migrations",
"migrations2": "migrations2.test_migrations_2",

25
tests/migrations/test_migrations_atomic_operation/0001_initial.py Normal file
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@ -0,0 +1,25 @@
# -*- coding: utf-8 -*-
from __future__ import unicode_literals
from django.db import migrations, models
def raise_error(apps, schema_editor):
# Test atomic operation in non-atomic migration is wrapped in transaction
Editor = apps.get_model('migrations', 'Editor')
Editor.objects.create(name='Test Editor')
raise RuntimeError('Abort migration')
class Migration(migrations.Migration):
atomic = False
operations = [
migrations.CreateModel(
"Editor",
[
("name", models.CharField(primary_key=True, max_length=255)),
],
),
migrations.RunPython(raise_error, atomic=True),
]

0
tests/migrations/test_migrations_atomic_operation/__init__.py Normal file
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32
tests/migrations/test_migrations_non_atomic/0001_initial.py Normal file
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@ -0,0 +1,32 @@
# -*- coding: utf-8 -*-
from __future__ import unicode_literals
from django.db import migrations, models
def raise_error(apps, schema_editor):
# Test operation in non-atomic migration is not wrapped in transaction
Publisher = apps.get_model('migrations', 'Publisher')
Publisher.objects.create(name='Test Publisher')
raise RuntimeError('Abort migration')
class Migration(migrations.Migration):
atomic = False
operations = [
migrations.CreateModel(
"Publisher",
[
("name", models.CharField(primary_key=True, max_length=255)),
],
),
migrations.RunPython(raise_error),
migrations.CreateModel(
"Book",
[
("title", models.CharField(primary_key=True, max_length=255)),
("publisher", models.ForeignKey("migrations.Publisher", models.SET_NULL, null=True)),
],
),
]

0
tests/migrations/test_migrations_non_atomic/__init__.py Normal file
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