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import json
import unittest
import xml.etree.ElementTree
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"),
]
if connection.features.supports_select_union:
querysets.append(
Tag.objects.order_by().union(Tag.objects.order_by().filter(name="test"))
)
if connection.features.has_select_for_update:
querysets.append(Tag.objects.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):
with self.assertNumQueries(1) 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)
if not format:
continue
if format.lower() == "xml":
try:
xml.etree.ElementTree.fromstring(result)
except xml.etree.ElementTree.ParseError as e:
self.fail(
f"QuerySet.explain() result is not valid XML: {e}"
)
elif format.lower() == "json":
try:
json.loads(result)
except json.JSONDecodeError as e:
self.fail(
f"QuerySet.explain() result is not valid JSON: {e}"
)
def test_unknown_options(self):
with self.assertRaisesMessage(ValueError, "Unknown options: TEST, TEST2"):
Tag.objects.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)
)
else:
msg += f" {connection.display_name} does not support any formats."
with self.assertRaisesMessage(ValueError, msg):
Tag.objects.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},
{"summary": True},
{"settings": True},
{"analyze": True, "wal": True},
]
if connection.features.is_postgresql_16:
test_options.append({"generic_plan": True})
if connection.features.is_postgresql_17:
test_options.append({"memory": True})
test_options.append({"serialize": "TEXT", "analyze": True})
test_options.append({"serialize": "text", "analyze": True})
test_options.append({"serialize": "BINARY", "analyze": True})
test_options.append({"serialize": "binary", "analyze": 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():
if isinstance(value, str):
option = "{} {}".format(name.upper(), value.upper())
else:
option = "{} {}".format(
name.upper(), "true" if value else "false"
)
self.assertIn(option, captured_queries[0]["sql"])
@skipUnlessDBFeature("supports_select_union")
def test_multi_page_text_explain(self):
if "TEXT" not in connection.features.supported_explain_formats:
self.skipTest("This backend does not support TEXT format.")
base_qs = Tag.objects.order_by()
qs = base_qs.filter(name="test").union(*[base_qs for _ in range(100)])
result = qs.explain(format="text")
self.assertGreaterEqual(result.count("\n"), 100)
def test_option_sql_injection(self):
qs = Tag.objects.filter(name="test")
options = {"SUMMARY true) SELECT 1; --": True}
msg = "Invalid option name: 'SUMMARY true) SELECT 1; --'"
with self.assertRaisesMessage(ValueError, msg):
qs.explain(**options)
def test_invalid_option_names(self):
qs = Tag.objects.filter(name="test")
tests = [
'opt"ion',
"o'ption",
"op`tion",
"opti on",
"option--",
"optio\tn",
"o\nption",
"option;",
"你 好",
# [] are used by MSSQL.
"option[",
"option]",
]
for invalid_option in tests:
with self.subTest(invalid_option):
msg = f"Invalid option name: {invalid_option!r}"
with self.assertRaisesMessage(ValueError, msg):
qs.explain(**{invalid_option: True})
@unittest.skipUnless(connection.vendor == "mysql", "MySQL specific")
def test_mysql_text_to_traditional(self):
# Ensure these cached properties are initialized to prevent queries for
# the MariaDB or MySQL version during the QuerySet evaluation.
connection.features.supported_explain_formats
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", "MariaDB and MySQL >= 8.0.18 specific."
)
def test_mysql_analyze(self):
qs = Tag.objects.filter(name="test")
with CaptureQueriesContext(connection) as captured_queries:
qs.explain(analyze=True)
self.assertEqual(len(captured_queries), 1)
prefix = "ANALYZE " if connection.mysql_is_mariadb else "EXPLAIN ANALYZE "
self.assertTrue(captured_queries[0]["sql"].startswith(prefix))
with CaptureQueriesContext(connection) as captured_queries:
qs.explain(analyze=True, format="JSON")
self.assertEqual(len(captured_queries), 1)
if connection.mysql_is_mariadb:
self.assertIn("FORMAT=JSON", captured_queries[0]["sql"])
else:
self.assertNotIn("FORMAT=JSON", 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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