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import unittest
from django.db import NotSupportedError, connection, transaction
from django.db.models import Count
from django.test import TestCase, skipIfDBFeature, skipUnlessDBFeature
from django.test.utils import CaptureQueriesContext
from .models import Tag
@skipUnlessDBFeature('supports_explaining_query_execution')
class ExplainTests(TestCase):
def test_basic(self):
querysets = [
Tag.objects.filter(name='test'),
Tag.objects.filter(name='test').select_related('parent'),
Tag.objects.filter(name='test').prefetch_related('children'),
Tag.objects.filter(name='test').annotate(Count('children')),
Tag.objects.filter(name='test').values_list('name'),
Tag.objects.order_by().union(Tag.objects.order_by().filter(name='test')),
Tag.objects.all().select_for_update().filter(name='test'),
]
supported_formats = connection.features.supported_explain_formats
all_formats = (None,) + tuple(supported_formats) + tuple(f.lower() for f in supported_formats)
for idx, queryset in enumerate(querysets):
for format in all_formats:
with self.subTest(format=format, queryset=idx):
if connection.vendor == 'mysql':
# This does a query and caches the result.
connection.features.needs_explain_extended
with self.assertNumQueries(1), CaptureQueriesContext(connection) as captured_queries:
result = queryset.explain(format=format)
self.assertTrue(captured_queries[0]['sql'].startswith(connection.ops.explain_prefix))
self.assertIsInstance(result, str)
self.assertTrue(result)
@skipUnlessDBFeature('validates_explain_options')
def test_unknown_options(self):
with self.assertRaisesMessage(ValueError, 'Unknown options: test, test2'):
Tag.objects.all().explain(test=1, test2=1)
def test_unknown_format(self):
msg = 'DOES NOT EXIST is not a recognized format.'
if connection.features.supported_explain_formats:
msg += ' Allowed formats: %s' % ', '.join(sorted(connection.features.supported_explain_formats))
with self.assertRaisesMessage(ValueError, msg):
Tag.objects.all().explain(format='does not exist')
@unittest.skipUnless(connection.vendor == 'postgresql', 'PostgreSQL specific')
def test_postgres_options(self):
qs = Tag.objects.filter(name='test')
test_options = [
{'COSTS': False, 'BUFFERS': True, 'ANALYZE': True},
{'costs': False, 'buffers': True, 'analyze': True},
{'verbose': True, 'timing': True, 'analyze': True},
{'verbose': False, 'timing': False, 'analyze': True},
]
if connection.pg_version >= 100000:
test_options.append({'summary': True})
for options in test_options:
with self.subTest(**options), transaction.atomic():
with CaptureQueriesContext(connection) as captured_queries:
qs.explain(format='text', **options)
self.assertEqual(len(captured_queries), 1)
for name, value in options.items():
option = '{} {}'.format(name.upper(), 'true' if value else 'false')
self.assertIn(option, captured_queries[0]['sql'])
@unittest.skipUnless(connection.vendor == 'mysql', 'MySQL specific')
def test_mysql_text_to_traditional(self):
# Initialize the cached property, if needed, to prevent a query for
# the MySQL version during the QuerySet evaluation.
connection.features.needs_explain_extended
with CaptureQueriesContext(connection) as captured_queries:
Tag.objects.filter(name='test').explain(format='text')
self.assertEqual(len(captured_queries), 1)
self.assertIn('FORMAT=TRADITIONAL', captured_queries[0]['sql'])
@unittest.skipUnless(connection.vendor == 'mysql', 'MySQL < 5.7 specific')
def test_mysql_extended(self):
# Inner skip to avoid module level query for MySQL version.
if not connection.features.needs_explain_extended:
raise unittest.SkipTest('MySQL < 5.7 specific')
qs = Tag.objects.filter(name='test')
with CaptureQueriesContext(connection) as captured_queries:
qs.explain(format='json')
self.assertEqual(len(captured_queries), 1)
self.assertNotIn('EXTENDED', captured_queries[0]['sql'])
with CaptureQueriesContext(connection) as captured_queries:
qs.explain(format='text')
self.assertEqual(len(captured_queries), 1)
self.assertNotIn('EXTENDED', captured_queries[0]['sql'])
@skipIfDBFeature('supports_explaining_query_execution')
class ExplainUnsupportedTests(TestCase):
def test_message(self):
msg = 'This backend does not support explaining query execution.'
with self.assertRaisesMessage(NotSupportedError, msg):
Tag.objects.filter(name='test').explain()
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