按计算(extra())字段筛选

有人知道通过extra()方法添加的字段过滤查询集的方法吗?

例如,这就是我想做的

_list_items = ListItem.objects.filter(list=1).extra(select=
      'SELECT value AS "type" FROM list_item_optional 
       WHERE list_item_optional.list_optional_id=1 
       AND list_item_optional.list_item_id = list_item.id')
_list_items = _list_items.filter(type='A')

我知道上面的情况是不允许的,但是在姜戈有什么解决办法呢?

同样,也不允许使用原始的SQL方法,例如: SELECT fieldA, fieldB, (SELECT blahblah from tableY WHERE id=1) AS "bla" FROM tableX WHERE "bla" = 'x'

Postgres中不允许按计算字段过滤…有人需要解决吗?由于by sql语句(queryset retrieves)是动态的,并且只在运行时定义,所以问题变得更大。

干杯

连接模型:

class List(models.Model):
    account = models.ForeignKey(Account)
    created_date = models.DateTimeField(auto_now_add=True)
    created_by = models.ForeignKey(AccountUser, related_name='x10')
    updated_date = models.DateTimeField(null=True, blank=True)
    updated_by = models.ForeignKey(AccountUser, null=True, blank=True, related_name='x11')
    is_deleted = models.BooleanField(default=False)
    name = models.CharField(max_length=50)

    objects_active = DeletedManager()

    class Meta:
        db_table = u'list'

class ListItem(models.Model):
    list = models.ForeignKey(List, db_index=True)
    key = models.CharField(max_length=50)
    name = models.CharField(max_length=100)

    class Meta:
        db_table = u'list_item'
        unique_together = ("list", "key")


class ListOptional(models.Model):
    list = models.ForeignKey(List, db_index=True)
    name = models.CharField(max_length=50)
    is_searchable = models.BooleanField()

    class Meta:
        db_table = u'list_optional'


class ListItemOptional(models.Model):
    list_item = models.ForeignKey(ListItem, null=True, db_index=True)
    list_optional = models.ForeignKey(ListOptional, null=True)
    value = models.CharField(max_length=100)

    class Meta:
        db_table = u'list_item_optional'