Django 来自 AN 操作和顺序过滤器的不同结果

Question

如果我有这样的模型：

class Person(models.Model):
    first_name = models.CharField(max_length=20)
    last_name = models.CharField(max_length=20)

class PersonSession(models.Model):
    start_time = models.DateTimeField(auto_now_add=True)
    end_time = models.DateTimeField(null=True,
                                    blank=True)
    person = models.ForeignKey(Person, related_name='sessions')

class Billing(models.Model):
    DEBT = 'DE'
    BALANCED = 'BA'
    CREDIT = 'CR'

    session = models.OneToOneField(PersonSession,
                                   blank=False,
                                   null=False,
                                   related_name='billing')
    STATUS = ((BALANCED, 'Balanced'),
              (DEBT, 'Debt'),
              (CREDIT, 'Credit'))

    status = models.CharField(max_length=2,
                              choices=STATUS,
                              blank=False,
                              default=BALANCED
                              )

以下两个查询生成不同的结果：

Person.objects.filter(Q(sessions__start_time__gte='2000-02-01') & \
                      Q(sessions__start_time__lte='2000-03-01') & \
                      Q(sessions__billing__status=Billing.DEBT))
OR
Person.objects.filter(Q(sessions__start_time__gte='2000-02-01') & \
                      Q(sessions__start_time__lte='2000-03-01')).filter(
                      Q(sessions__billing__status=Billing.DEBT))

第一个生成两个人1,2，第二个生成我所有的三个人，数据如下：

id | first_name | last_name | id |        start_time         |         end_time          | person_id | id | status | session_id 
---+------------+-----------+----+---------------------------+---------------------------+-----------+----+--------+------------
0 | person     | 0         |  0 | 2000-01-01 16:32:00+03:30 | 2000-01-01 17:32:00+03:30 |         0 |  0 | DE     |          0
0 | person     | 0         |  1 | 2000-02-01 16:32:00+03:30 | 2000-02-01 17:32:00+03:30 |         0 |  1 | BA     |          1
0 | person     | 0         |  2 | 2000-03-01 16:32:00+03:30 | 2000-03-01 17:32:00+03:30 |         0 |  2 | DE     |          2
1 | person     | 1         |  3 | 2000-01-01 16:32:00+03:30 | 2000-01-01 17:32:00+03:30 |         1 |  3 | BA     |          3
1 | person     | 1         |  4 | 2000-02-01 16:32:00+03:30 | 2000-02-01 17:32:00+03:30 |         1 |  4 | DE     |          4
1 | person     | 1         |  5 | 2000-03-01 16:32:00+03:30 | 2000-03-01 17:32:00+03:30 |         1 |  5 | DE     |          5
2 | person     | 2         |  6 | 2000-01-01 16:32:00+03:30 | 2000-01-01 17:32:00+03:30 |         2 |  6 | DE     |          6
2 | person     | 2         |  7 | 2000-02-01 16:32:00+03:30 | 2000-02-01 17:32:00+03:30 |         2 |  7 | DE     |          7
2 | person     | 2         |  8 | 2000-03-01 16:32:00+03:30 | 2000-03-01 17:32:00+03:30 |         2 |  8 | BA     |          8

我写了一个 example 来创建 class 和数据让他们显示差异。

请解释这两个查询之间的区别，作为附带问题，如果在 django-filter 包中我想定义一些字段作为第一个过滤器，我该怎么做？

Answer 1

过滤器生成的查询不同如下：

>>> print Person.objects.filter(Q(sessions__start_time__gte='2000-02-01') & \
...                       Q(sessions__start_time__lte='2000-03-01')).filter(
...                       Q(sessions__billing__status=Billing.DEBT)).query
SELECT "test_filter_person"."id", "test_filter_person"."first_name", "test_filter_person"."last_name" FROM "test_filter_person" INNER JOIN "test_filter_personsession" ON ("test_filter_person"."id" = "test_filter_personsession"."person_id") INNER JOIN "test_filter_personsession" T3 ON ("test_filter_person"."id" = T3."person_id") INNER JOIN "test_filter_billing" ON (T3."id" = "test_filter_billing"."session_id") WHERE ("test_filter_personsession"."start_time" >= 2000-02-01 00:00:00+00:00 AND "test_filter_personsession"."start_time" <= 2000-03-01 00:00:00+00:00 AND "test_filter_billing"."status" = DE)
>>> print Person.objects.filter(Q(sessions__start_time__gte='2000-02-01') & \
...                       Q(sessions__start_time__lte='2000-03-01') & \
...                       Q(sessions__billing__status=Billing.DEBT)).query
SELECT "test_filter_person"."id", "test_filter_person"."first_name", "test_filter_person"."last_name" FROM "test_filter_person" INNER JOIN "test_filter_personsession" ON ("test_filter_person"."id" = "test_filter_personsession"."person_id") INNER JOIN "test_filter_billing" ON ("test_filter_personsession"."id" = "test_filter_billing"."session_id") WHERE ("test_filter_personsession"."start_time" >= 2000-02-01 00:00:00+00:00 AND "test_filter_personsession"."start_time" <= 2000-03-01 00:00:00+00:00 AND "test_filter_billing"."status" = DE)

我们分别称它们为Q1和Q2。

如您所见，Q1 在 Person、PersonSession 和 Billing 之间进行了一次连接，并且所有条件都在 WHERE 子句中一起应用.

但是，在第 2 季度，由于您使用前两次检查终止了第一个过滤器，因此这导致 Person 和 PersonSession 之间的第一个查询连接首先出现（对于 Person.objects.filter(Q(sessions__start_time__gte='2000-02-01') & Q(sessions__start_time__lte='2000-03-01'))，第一个连接的结果再次与 PersonSession 和 Billing 连接，以执行过滤器查询的第二部分 .filter(Q(sessions__billing__status=Billing.DEBT)).

您可以在此处阅读更多内容：difference between filter with multiple arguments and chain filter in django

还想提请您注意post的最后一行：

One table: But if the query doesn't involve joined tables like the example from Yuji and DTing. The result is same.

Django 来自 AN 操作和顺序过滤器的不同结果

Django diffrenet results from AND operation and sequential filter

django

django-models

django-queryset

django-filters