447 lines
18 KiB
Python
447 lines
18 KiB
Python
import threading
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import time
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from unittest import mock
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from multiple_database.routers import TestRouter
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from django.core.exceptions import FieldError
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from django.db import (
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DatabaseError, NotSupportedError, connection, connections, router,
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transaction,
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)
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from django.test import (
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TransactionTestCase, override_settings, skipIfDBFeature,
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skipUnlessDBFeature,
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)
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from django.test.utils import CaptureQueriesContext
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from .models import City, Country, Person, PersonProfile
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class SelectForUpdateTests(TransactionTestCase):
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available_apps = ['select_for_update']
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def setUp(self):
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# This is executed in autocommit mode so that code in
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# run_select_for_update can see this data.
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self.country1 = Country.objects.create(name='Belgium')
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self.country2 = Country.objects.create(name='France')
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self.city1 = City.objects.create(name='Liberchies', country=self.country1)
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self.city2 = City.objects.create(name='Samois-sur-Seine', country=self.country2)
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self.person = Person.objects.create(name='Reinhardt', born=self.city1, died=self.city2)
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self.person_profile = PersonProfile.objects.create(person=self.person)
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# We need another database connection in transaction to test that one
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# connection issuing a SELECT ... FOR UPDATE will block.
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self.new_connection = connection.copy()
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def tearDown(self):
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try:
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self.end_blocking_transaction()
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except (DatabaseError, AttributeError):
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pass
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self.new_connection.close()
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def start_blocking_transaction(self):
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self.new_connection.set_autocommit(False)
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# Start a blocking transaction. At some point,
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# end_blocking_transaction() should be called.
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self.cursor = self.new_connection.cursor()
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sql = 'SELECT * FROM %(db_table)s %(for_update)s;' % {
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'db_table': Person._meta.db_table,
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'for_update': self.new_connection.ops.for_update_sql(),
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}
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self.cursor.execute(sql, ())
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self.cursor.fetchone()
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def end_blocking_transaction(self):
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# Roll back the blocking transaction.
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self.cursor.close()
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self.new_connection.rollback()
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self.new_connection.set_autocommit(True)
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def has_for_update_sql(self, queries, **kwargs):
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# Examine the SQL that was executed to determine whether it
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# contains the 'SELECT..FOR UPDATE' stanza.
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for_update_sql = connection.ops.for_update_sql(**kwargs)
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return any(for_update_sql in query['sql'] for query in queries)
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@skipUnlessDBFeature('has_select_for_update')
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def test_for_update_sql_generated(self):
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"""
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The backend's FOR UPDATE variant appears in
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generated SQL when select_for_update is invoked.
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"""
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with transaction.atomic(), CaptureQueriesContext(connection) as ctx:
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list(Person.objects.all().select_for_update())
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self.assertTrue(self.has_for_update_sql(ctx.captured_queries))
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@skipUnlessDBFeature('has_select_for_update_nowait')
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def test_for_update_sql_generated_nowait(self):
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"""
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The backend's FOR UPDATE NOWAIT variant appears in
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generated SQL when select_for_update is invoked.
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"""
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with transaction.atomic(), CaptureQueriesContext(connection) as ctx:
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list(Person.objects.all().select_for_update(nowait=True))
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self.assertTrue(self.has_for_update_sql(ctx.captured_queries, nowait=True))
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@skipUnlessDBFeature('has_select_for_update_skip_locked')
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def test_for_update_sql_generated_skip_locked(self):
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"""
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The backend's FOR UPDATE SKIP LOCKED variant appears in
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generated SQL when select_for_update is invoked.
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"""
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with transaction.atomic(), CaptureQueriesContext(connection) as ctx:
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list(Person.objects.all().select_for_update(skip_locked=True))
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self.assertTrue(self.has_for_update_sql(ctx.captured_queries, skip_locked=True))
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@skipUnlessDBFeature('has_select_for_update_of')
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def test_for_update_sql_generated_of(self):
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"""
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The backend's FOR UPDATE OF variant appears in the generated SQL when
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select_for_update() is invoked.
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"""
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with transaction.atomic(), CaptureQueriesContext(connection) as ctx:
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list(Person.objects.select_related(
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'born__country',
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).select_for_update(
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of=('born__country',),
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).select_for_update(
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of=('self', 'born__country')
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))
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features = connections['default'].features
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if features.select_for_update_of_column:
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expected = ['select_for_update_person"."id', 'select_for_update_country"."id']
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else:
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expected = ['select_for_update_person', 'select_for_update_country']
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expected = [connection.ops.quote_name(value) for value in expected]
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self.assertTrue(self.has_for_update_sql(ctx.captured_queries, of=expected))
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@skipUnlessDBFeature('has_select_for_update_of')
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def test_for_update_of_followed_by_values(self):
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with transaction.atomic():
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values = list(Person.objects.select_for_update(of=('self',)).values('pk'))
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self.assertEqual(values, [{'pk': self.person.pk}])
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@skipUnlessDBFeature('has_select_for_update_of')
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def test_for_update_of_followed_by_values_list(self):
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with transaction.atomic():
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values = list(Person.objects.select_for_update(of=('self',)).values_list('pk'))
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self.assertEqual(values, [(self.person.pk,)])
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@skipUnlessDBFeature('has_select_for_update_of')
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def test_for_update_of_self_when_self_is_not_selected(self):
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"""
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select_for_update(of=['self']) when the only columns selected are from
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related tables.
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"""
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with transaction.atomic():
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values = list(Person.objects.select_related('born').select_for_update(of=('self',)).values('born__name'))
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self.assertEqual(values, [{'born__name': self.city1.name}])
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@skipUnlessDBFeature('has_select_for_update_nowait')
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def test_nowait_raises_error_on_block(self):
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"""
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If nowait is specified, we expect an error to be raised rather
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than blocking.
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"""
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self.start_blocking_transaction()
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status = []
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thread = threading.Thread(
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target=self.run_select_for_update,
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args=(status,),
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kwargs={'nowait': True},
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)
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thread.start()
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time.sleep(1)
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thread.join()
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self.end_blocking_transaction()
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self.assertIsInstance(status[-1], DatabaseError)
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@skipUnlessDBFeature('has_select_for_update_skip_locked')
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def test_skip_locked_skips_locked_rows(self):
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"""
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If skip_locked is specified, the locked row is skipped resulting in
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Person.DoesNotExist.
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"""
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self.start_blocking_transaction()
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status = []
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thread = threading.Thread(
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target=self.run_select_for_update,
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args=(status,),
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kwargs={'skip_locked': True},
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)
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thread.start()
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time.sleep(1)
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thread.join()
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self.end_blocking_transaction()
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self.assertIsInstance(status[-1], Person.DoesNotExist)
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@skipIfDBFeature('has_select_for_update_nowait')
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@skipUnlessDBFeature('has_select_for_update')
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def test_unsupported_nowait_raises_error(self):
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"""
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NotSupportedError is raised if a SELECT...FOR UPDATE NOWAIT is run on
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a database backend that supports FOR UPDATE but not NOWAIT.
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"""
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with self.assertRaisesMessage(NotSupportedError, 'NOWAIT is not supported on this database backend.'):
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with transaction.atomic():
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Person.objects.select_for_update(nowait=True).get()
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@skipIfDBFeature('has_select_for_update_skip_locked')
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@skipUnlessDBFeature('has_select_for_update')
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def test_unsupported_skip_locked_raises_error(self):
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"""
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NotSupportedError is raised if a SELECT...FOR UPDATE SKIP LOCKED is run
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on a database backend that supports FOR UPDATE but not SKIP LOCKED.
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"""
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with self.assertRaisesMessage(NotSupportedError, 'SKIP LOCKED is not supported on this database backend.'):
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with transaction.atomic():
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Person.objects.select_for_update(skip_locked=True).get()
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@skipIfDBFeature('has_select_for_update_of')
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@skipUnlessDBFeature('has_select_for_update')
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def test_unsupported_of_raises_error(self):
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"""
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NotSupportedError is raised if a SELECT...FOR UPDATE OF... is run on
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a database backend that supports FOR UPDATE but not OF.
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"""
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msg = 'FOR UPDATE OF is not supported on this database backend.'
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with self.assertRaisesMessage(NotSupportedError, msg):
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with transaction.atomic():
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Person.objects.select_for_update(of=('self',)).get()
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@skipUnlessDBFeature('has_select_for_update', 'has_select_for_update_of')
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def test_unrelated_of_argument_raises_error(self):
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"""
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FieldError is raised if a non-relation field is specified in of=(...).
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"""
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msg = (
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'Invalid field name(s) given in select_for_update(of=(...)): %s. '
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'Only relational fields followed in the query are allowed. '
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'Choices are: self, born, born__country.'
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)
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invalid_of = [
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('nonexistent',),
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('name',),
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('born__nonexistent',),
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('born__name',),
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('born__nonexistent', 'born__name'),
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]
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for of in invalid_of:
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with self.subTest(of=of):
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with self.assertRaisesMessage(FieldError, msg % ', '.join(of)):
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with transaction.atomic():
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Person.objects.select_related('born__country').select_for_update(of=of).get()
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@skipUnlessDBFeature('has_select_for_update', 'has_select_for_update_of')
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def test_related_but_unselected_of_argument_raises_error(self):
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"""
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FieldError is raised if a relation field that is not followed in the
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query is specified in of=(...).
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"""
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msg = (
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'Invalid field name(s) given in select_for_update(of=(...)): %s. '
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'Only relational fields followed in the query are allowed. '
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'Choices are: self, born, profile.'
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)
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for name in ['born__country', 'died', 'died__country']:
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with self.subTest(name=name):
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with self.assertRaisesMessage(FieldError, msg % name):
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with transaction.atomic():
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Person.objects.select_related(
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'born', 'profile',
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).exclude(profile=None).select_for_update(of=(name,)).get()
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@skipUnlessDBFeature('has_select_for_update', 'has_select_for_update_of')
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def test_reverse_one_to_one_of_arguments(self):
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"""
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Reverse OneToOneFields may be included in of=(...) as long as NULLs
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are excluded because LEFT JOIN isn't allowed in SELECT FOR UPDATE.
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"""
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with transaction.atomic():
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person = Person.objects.select_related(
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'profile',
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).exclude(profile=None).select_for_update(of=('profile',)).get()
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self.assertEqual(person.profile, self.person_profile)
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@skipUnlessDBFeature('has_select_for_update')
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def test_for_update_after_from(self):
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features_class = connections['default'].features.__class__
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attribute_to_patch = "%s.%s.for_update_after_from" % (features_class.__module__, features_class.__name__)
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with mock.patch(attribute_to_patch, return_value=True):
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with transaction.atomic():
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self.assertIn('FOR UPDATE WHERE', str(Person.objects.filter(name='foo').select_for_update().query))
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@skipUnlessDBFeature('has_select_for_update')
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def test_for_update_requires_transaction(self):
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"""
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A TransactionManagementError is raised
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when a select_for_update query is executed outside of a transaction.
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"""
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msg = 'select_for_update cannot be used outside of a transaction.'
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with self.assertRaisesMessage(transaction.TransactionManagementError, msg):
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list(Person.objects.all().select_for_update())
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@skipUnlessDBFeature('has_select_for_update')
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def test_for_update_requires_transaction_only_in_execution(self):
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"""
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No TransactionManagementError is raised
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when select_for_update is invoked outside of a transaction -
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only when the query is executed.
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"""
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people = Person.objects.all().select_for_update()
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msg = 'select_for_update cannot be used outside of a transaction.'
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with self.assertRaisesMessage(transaction.TransactionManagementError, msg):
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list(people)
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@skipUnlessDBFeature('supports_select_for_update_with_limit')
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def test_select_for_update_with_limit(self):
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other = Person.objects.create(name='Grappeli', born=self.city1, died=self.city2)
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with transaction.atomic():
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qs = list(Person.objects.all().order_by('pk').select_for_update()[1:2])
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self.assertEqual(qs[0], other)
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@skipIfDBFeature('supports_select_for_update_with_limit')
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def test_unsupported_select_for_update_with_limit(self):
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msg = 'LIMIT/OFFSET is not supported with select_for_update on this database backend.'
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with self.assertRaisesMessage(NotSupportedError, msg):
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with transaction.atomic():
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list(Person.objects.all().order_by('pk').select_for_update()[1:2])
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def run_select_for_update(self, status, **kwargs):
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"""
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Utility method that runs a SELECT FOR UPDATE against all
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Person instances. After the select_for_update, it attempts
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to update the name of the only record, save, and commit.
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This function expects to run in a separate thread.
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"""
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status.append('started')
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try:
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# We need to enter transaction management again, as this is done on
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# per-thread basis
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with transaction.atomic():
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person = Person.objects.select_for_update(**kwargs).get()
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person.name = 'Fred'
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person.save()
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except (DatabaseError, Person.DoesNotExist) as e:
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status.append(e)
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finally:
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# This method is run in a separate thread. It uses its own
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# database connection. Close it without waiting for the GC.
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connection.close()
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@skipUnlessDBFeature('has_select_for_update')
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@skipUnlessDBFeature('supports_transactions')
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def test_block(self):
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"""
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A thread running a select_for_update that accesses rows being touched
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by a similar operation on another connection blocks correctly.
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"""
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# First, let's start the transaction in our thread.
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self.start_blocking_transaction()
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# Now, try it again using the ORM's select_for_update
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# facility. Do this in a separate thread.
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status = []
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thread = threading.Thread(
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target=self.run_select_for_update, args=(status,)
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)
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# The thread should immediately block, but we'll sleep
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# for a bit to make sure.
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thread.start()
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sanity_count = 0
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while len(status) != 1 and sanity_count < 10:
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sanity_count += 1
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time.sleep(1)
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if sanity_count >= 10:
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raise ValueError('Thread did not run and block')
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# Check the person hasn't been updated. Since this isn't
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# using FOR UPDATE, it won't block.
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p = Person.objects.get(pk=self.person.pk)
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self.assertEqual('Reinhardt', p.name)
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# When we end our blocking transaction, our thread should
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# be able to continue.
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self.end_blocking_transaction()
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thread.join(5.0)
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# Check the thread has finished. Assuming it has, we should
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# find that it has updated the person's name.
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self.assertFalse(thread.is_alive())
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# We must commit the transaction to ensure that MySQL gets a fresh read,
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# since by default it runs in REPEATABLE READ mode
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transaction.commit()
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p = Person.objects.get(pk=self.person.pk)
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self.assertEqual('Fred', p.name)
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@skipUnlessDBFeature('has_select_for_update')
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def test_raw_lock_not_available(self):
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"""
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Running a raw query which can't obtain a FOR UPDATE lock raises
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the correct exception
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"""
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self.start_blocking_transaction()
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def raw(status):
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try:
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list(
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Person.objects.raw(
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'SELECT * FROM %s %s' % (
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Person._meta.db_table,
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connection.ops.for_update_sql(nowait=True)
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)
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)
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)
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except DatabaseError as e:
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status.append(e)
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finally:
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# This method is run in a separate thread. It uses its own
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# database connection. Close it without waiting for the GC.
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# Connection cannot be closed on Oracle because cursor is still
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# open.
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if connection.vendor != 'oracle':
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connection.close()
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status = []
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thread = threading.Thread(target=raw, kwargs={'status': status})
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thread.start()
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time.sleep(1)
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thread.join()
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self.end_blocking_transaction()
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self.assertIsInstance(status[-1], DatabaseError)
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@skipUnlessDBFeature('has_select_for_update')
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@override_settings(DATABASE_ROUTERS=[TestRouter()])
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def test_select_for_update_on_multidb(self):
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query = Person.objects.select_for_update()
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self.assertEqual(router.db_for_write(Person), query.db)
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@skipUnlessDBFeature('has_select_for_update')
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def test_select_for_update_with_get(self):
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with transaction.atomic():
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person = Person.objects.select_for_update().get(name='Reinhardt')
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self.assertEqual(person.name, 'Reinhardt')
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def test_nowait_and_skip_locked(self):
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with self.assertRaisesMessage(ValueError, 'The nowait option cannot be used with skip_locked.'):
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Person.objects.select_for_update(nowait=True, skip_locked=True)
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def test_ordered_select_for_update(self):
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"""
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Subqueries should respect ordering as an ORDER BY clause may be useful
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to specify a row locking order to prevent deadlocks (#27193).
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"""
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with transaction.atomic():
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qs = Person.objects.filter(id__in=Person.objects.order_by('-id').select_for_update())
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self.assertIn('ORDER BY', str(qs.query))
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