我试图找出实用函数执行的查询数量。我已经为此函数编写了单元测试,并且该函数运行良好。我想做的是跟踪函数执行的 SQL 查询的数量,以便我可以看到重构后是否有任何改进。
def do_something_in_the_database():
# Does something in the database
# return result
class DoSomethingTests(django.test.TestCase):
def test_function_returns_correct_values(self):
self.assertEqual(n, <number of SQL queries executed>)
编辑:我发现有一个待处理的 Django 功能请求。然而,票仍然开放。与此同时,还有其他方法可以解决这个问题吗?
自 Django 1.3 起,就有了一个 assertNumQueries 专门用于此目的。
使用它的一种方法(从 Django 3.2 开始)是作为上下文管理器:
# measure queries of some_func and some_func2
with self.assertNumQueries(2):
result = some_func()
result2 = some_func2()
Vinay 的回答是正确的,但有一点补充。
Django 的单元测试框架实际上在运行时将 DEBUG 设置为 False,因此无论
settings.py
中有什么,单元测试中的 connection.queries
中都不会填充任何内容,除非重新启用调试模式。 Django 文档将其原理解释为:
无论配置文件中 DEBUG 设置的值如何,所有 Django 测试都以 DEBUG=False 运行。这是为了确保观察到的代码输出与生产环境中看到的输出相匹配。如果您确定启用调试不会影响您的测试(例如,如果您专门测试数据库命中,就像听起来的那样),解决方案是暂时在单元测试中重新启用调试,然后设置之后又回来了:
def test_myself(self):
from django.conf import settings
from django.db import connection
settings.DEBUG = True
connection.queries = []
# Test code as normal
self.assert_(connection.queries)
settings.DEBUG = False
pytest
,
pytest-django
有用于此目的的django_assert_num_queries 固定装置:
def test_queries(django_assert_num_queries):
with django_assert_num_queries(3):
Item.objects.create('foo')
Item.objects.create('bar')
Item.objects.create('baz')
assertNumQueries)或将设置更改为 DEBUG=True,则可以使用上下文管理器 CaptureQueriesContext(与 assertNumQueries 使用相同)。
from django.db import ConnectionHandler
from django.test.utils import CaptureQueriesContext
DB_NAME = "default" # name of db configured in settings you want to use - "default" is standard
connection = ConnectionHandler()[DB_NAME]
with CaptureQueriesContext(connection) as context:
... # do your thing
num_queries = context.initial_queries - context.final_queries
assert num_queries == expected_num_queries
here,您可以使用方法 reset_queries,而不是分配 connection.queries=[],这确实会引发错误,例如适用于 django>=1.8:
class QueriesTests(django.test.TestCase):
def test_queries(self):
from django.conf import settings
from django.db import connection, reset_queries
try:
settings.DEBUG = True
# [... your ORM code ...]
self.assertEquals(len(connection.queries), num_of_expected_queries)
finally:
settings.DEBUG = False
reset_queries()
您还可以考虑在setUp/tearDown上重置查询,以确保为每个测试重置查询,而不是在finally子句上执行,但这种方式更明确(尽管更冗长),或者您可以在try子句中使用
reset_queries您需要评估从 0 开始计算的查询的次数。
上下文管理器的工作原型
import json
from contextlib import contextmanager
from django.test.utils import CaptureQueriesContext
from django.db import connections
@contextmanager
def withAssertNumQueriesLessThan(self, value, using='default', verbose=False):
with CaptureQueriesContext(connections[using]) as context:
yield # your test will be run here
if verbose:
msg = "\r\n%s" % json.dumps(context.captured_queries, indent=4)
else:
msg = None
self.assertLess(len(context.captured_queries), value, msg=msg)
它可以简单地用在您的单元测试中,例如检查每个 Django REST API 调用的查询数量
with self.withAssertNumQueriesLessThan(10):
response = self.client.get('contacts/')
self.assertEqual(response.status_code, 200)
如果您想要将实际查询的列表漂亮地打印到标准输出,您还可以提供准确的数据库
using
和verbose
DEBUG
中将
settings.py
设置为 True(大概在您的测试环境中如此),那么您可以按如下方式对测试中执行的查询进行计数:
from django.db import connection
class DoSomethingTests(django.test.TestCase):
def test_something_or_other(self):
num_queries_old = len(connection.queries)
do_something_in_the_database()
num_queries_new = len(connection.queries)
self.assertEqual(n, num_queries_new - num_queries_old)
很好的要点:
import functools
import sys
import re
from django.conf import settings
from django.db import connection
def shrink_select(sql):
return re.sub("^SELECT(.+)FROM", "SELECT .. FROM", sql)
def shrink_update(sql):
return re.sub("SET(.+)WHERE", "SET .. WHERE", sql)
def shrink_insert(sql):
return re.sub("\((.+)\)", "(..)", sql)
def shrink_sql(sql):
return shrink_update(shrink_insert(shrink_select(sql)))
def _err_msg(num, expected_num, verbose, func=None):
func_name = "%s:" % func.__name__ if func else ""
msg = "%s Expected number of queries is %d, actual number is %d.\n" % (func_name, expected_num, num,)
if verbose > 0:
queries = [query['sql'] for query in connection.queries[-num:]]
if verbose == 1:
queries = [shrink_sql(sql) for sql in queries]
msg += "== Queries == \n" +"\n".join(queries)
return msg
def assertNumQueries(expected_num, verbose=1):
class DecoratorOrContextManager(object):
def __call__(self, func): # decorator
@functools.wraps(func)
def inner(*args, **kwargs):
handled = False
try:
self.__enter__()
return func(*args, **kwargs)
except:
self.__exit__(*sys.exc_info())
handled = True
raise
finally:
if not handled:
self.__exit__(None, None, None)
return inner
def __enter__(self):
self.old_debug = settings.DEBUG
self.old_query_count = len(connection.queries)
settings.DEBUG = True
def __exit__(self, type, value, traceback):
if not type:
num = len(connection.queries) - self.old_query_count
assert expected_num == num, _err_msg(num, expected_num, verbose)
settings.DEBUG = self.old_debug
return DecoratorOrContextManager()