Create a gist now

Instantly share code, notes, and snippets.

What would you like to do?
assertNumQueries decorator and context manager
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()
# usage
class MyTestCase(TestCase):
@assertNumQueries(5)
def test_1(self):
# ...
def test_2(self):
# ...
with assertNumQueries(3, verbose=2):
# ...
# ...
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment