Django 测试 - 外部修改数据时的多个查询。缓存问题？

Question

我有一个遗留应用程序（当前）使用 Django 来有效地显示数据。我的一项工作测试的示例如下所示。

def test_add_property_value(self):
    """Test set / get a value"""
    # This will do some external process which occcurs to the db.
    pm = Pm(mysql_db='test_bugs')
    tree =  pm.add_release_tree()
    prop_type, pmvalue = ("string", "Funny Business")
    pmproperty = "%s_%s_basic" % (tree[0].name, prop_type)
    pm.add_property_definition(pmproperty, prop_type=prop_type)
    pm.add_propval(pmproperty, value=pmvalue, project=tree[0].name)

    # Now use Django to pull the value back out..
    project = Project.objects.get(name=tree[0].name)
    property = project.get_property(pmproperty) # Custom query using sql.raw
    self.assertEqual(pmvalue, property.value)

正如您所看到的，这是基本的 A/B 测试。现在我发现了一个限制，并且我似乎无法解决多个外部添加-检查-循环查询失败的问题。修改上述代码失败，因为它似乎查询无法甚至运行。

def test_add_property_value(self):
    """Test set / get a value"""

    # This will do some external process which occcurs to the db.
    pm = Pm(mysql_db='test_bugs', p4_port = settings.ICMSERVER_TEST_PORT)
    tree = pm.add_release_tree()
    prop_type, pmvalue = ("string", "Funny Business")
    pmproperty = "%s_%s_basic" % (tree[1].name, prop_type)
    pm.add_property_definition(pmproperty, prop_type=prop_type)
    pm.add_propval(pmproperty, value=pmvalue, project=tree[1].name)

    # Now use Django to pull the value back out..
    project = Project.objects.get(name=tree[1].name)
    property = project.get_property(pmproperty)
    self.assertEqual(pmvalue, property.value)

    # ONLY CHANGE WAS TO ADD THIS..

    # This will do some external process which occcurs to the db.
    pmproperty = "%s_%s_basic_two" % (tree[1].name, prop_type)
    pm.add_property_definition(pmproperty, prop_type=prop_type)
    pm.add_propval(pmproperty, value=pmvalue, project=tree[1].name)

    # Now use Django to pull the value back out..
    project = Project.objects.get(name=tree[1].name)
    property = project.get_property(pmproperty)
    self.assertEqual(pmvalue, property.value)

我读过有关 CACHE_BACKEND 的内容，但没有似乎有帮助。还有其他想法吗？经过进一步调查，这似乎与我的外部数据库根本无关。啊..感觉就像星期一！

1. 这是缓存问题吗？顺便说一句 - 设置 CACHE_BACKEND = 'dummy:///' 或 'locmem:///' 没有执行任何操作。
2. 我如何更好地诊断这个问题？

谢谢

更新

这是最终答案 - 2 个小调整..基于 Daniel 和高级。非常感谢各位指点！！

class PropertyTests(TransactionTestCase):  #CHANGE1
    def test_add_property_value(self):
        """Test set / get a value"""

        import logging
        l = logging.getLogger('django.db.backends')
        l.setLevel(logging.DEBUG)
        l.addHandler(logging.StreamHandler())

        # This will do some external process which occcurs to the db.
        pm = Pm(mysql_db='test_bugs', p4_port = settings.ICMSERVER_TEST_PORT)
        tree = pm.add_release_tree()
        prop_type, pmvalue = ("string", "Funny Business")
        pmproperty = "%s_%s_basic" % (tree[1].name, prop_type)
        pm.add_property_definition(pmproperty, prop_type=prop_type)
        pm.add_propval(pmproperty, value=pmvalue, project=tree[1].name)

        # Now use Django to pull the value back out..
        project = Project.objects.get(name=tree[1].name)
        property = project.get_property(pmproperty)
        self.assertEqual(pmvalue, property.value)

        # This will do some external process which occcurs to the db.
        pmproperty = "%s_%s_basic_two" % (tree[1].name, prop_type)
        pm.add_property_definition(pmproperty, prop_type=prop_type)
        pm.add_propval(pmproperty, value=pmvalue, project=tree[1].name)

        # Now use Django to pull the value back out..
        Project.objects.update() #CHANGE2
        project = Project.objects.get(name=tree[1].name)
        property = project.get_property(pmproperty)
        self.assertEqual(pmvalue, property.value)

Answer 1

这可能不是交易问题。需要向管理器 (Project.objects) 通知数据更改，因为它被设计为仅存在很短的时间。

您正在查询两次相同的查询 Project.objects.get(name=tree[1].name) 并且管理器不会再次执行它，因为它认为它已经拥有正确的数据。

在第二个查询之前，使

Project.objects.update()

管理器缓存失效。无效后的结果应是最新的。