python - 覆盖 Django RelatedManager 和 Queryset 以过滤通过模型中的字段

Question

我有两个模型通过第三个模型通过多对多字段链接。Through 模型中有一些额外的字段。我想覆盖 RelatedManager 以生成一些自定义查询集，这些查询集使用通过模型中的额外字段。需要注意的是，我的通过模型是使用定义额外字段的子类/mixin 创建的。我想要做的是获取与 SampleBatch 相关的所有 Gene 对象，这些对象在链接多对多字段的 SampleBatchGene 实例中具有 1 的活动状态：

In [1]: SampleBatch.objects.get(sample__lab_number="18_11998").genes.active()                                                                                                        
Out[1]: <QuerySet [<Gene: BAP1>]>

这是我到目前为止所拥有的：

class SampleBatch(models.Model):
    sample = models.ForeignKey(Sample, on_delete=models.CASCADE)
    batch = models.ForeignKey(Batch, on_delete=models.CASCADE)
    genes = models.ManyToManyField(
        "Gene", through='SampleBatchGene', related_name='samplebatches',
        blank=True, through_fields=('samplebatch', 'gene')
    )

    class Meta:
        managed = True
        db_table = 'sample_batch'
        unique_together = (('sample', 'batch'),)
        verbose_name_plural = "Sample batches"

    def __str__(self):
        return '{}-{}'.format(self.sample, self.batch)


class Gene(models.Model):
    gene_id = models.BigAutoField(primary_key=True)
    gene_name = models.CharField(unique=True, max_length=255, db_index=True)
    hgnc_number = models.IntegerField(unique=True, db_index=True)

    class Meta:
        managed = True
        db_table = 'gene'

    def __str__(self):
        return self.gene_name


class ActiveQuerySet(models.QuerySet):
    def active(self):
        return self.filter(active=1)

    def inactive(self):
        return self.filter(active=0)

class LinkMixin(models.Model):
    ACTIVE_CHOICES = (
        (0, 'Inactive'),
        (1, 'Active')
    )

    activated = models.DateTimeField(default=timezone.now)
    active = models.IntegerField(
        choices=ACTIVE_CHOICES, default=1, db_index=True
    )
    created = models.DateTimeField(auto_now_add=True)
    deactivated = models.DateTimeField(blank=True, null=True, default=None)
    objects = models.Manager()
    statuses = ActiveQuerySet.as_manager()

    class Meta:
        abstract = True


class SampleBatchGene(LinkMixin):
    samplebatch = models.ForeignKey(SampleBatch, on_delete=models.CASCADE)
    gene = models.ForeignKey(Gene, on_delete=models.PROTECT)

    class Meta:
        managed = True
        db_table = 'sample_batch_gene'
        unique_together = (('samplebatch', 'gene'), )

    def __str__(self):
        return '{}-{}'.format(self.samplebatch, self.gene)

尝试使用自定义反向管理器（根据文档）会出现以下错误：

In [5]: SampleBatch.objects.get(sample__lab_number="18_11998").genes.all()                                                                                                                                    
Out[5]: <QuerySet [<Gene: BAP1>]>

In [6]: SampleBatch.objects.get(sample__lab_number="18_11998").genes.filter(samplebatchgene__active=1)                                                                                                        
Out[6]: <QuerySet [<Gene: BAP1>]>

In [7]: SampleBatch.objects.get(sample__lab_number="18_11998").genes(manager="statuses").active()                                                                                                             
---------------------------------------------------------------------------
AttributeError                            Traceback (most recent call last)
<ipython-input-6-d8d95f5854b4> in <module>
----> 1 SampleBatch.objects.get(sample__lab_number="18_11998").genes(manager="statuses").active()

~/.pyenv/versions/3.6.6/envs/varDB/lib/python3.6/site-packages/django/db/models/fields/related_descriptors.py in __call__(self, manager)
    848 
    849         def __call__(self, *, manager):
--> 850             manager = getattr(self.model, manager)
    851             manager_class = create_forward_many_to_many_manager(manager.__class__, rel, reverse)
    852             return manager_class(instance=self.instance)

AttributeError: type object 'Gene' has no attribute 'statuses'

编辑：Willem Van Onsem 提示：它正在尝试使用来自 的自定义管理器Gene，但我已针对SampleBatchGene. 所以我需要弄清楚如何从 Through Model 中指定自定义管理器。我曾希望通过 来完成这项工作，LinkMixin这样我就不必在Many-To-Many. 我想我可以将自定义管理器粘在两者上SampleBatch并Gene让它工作，但我有很多这种类型的关系使用LinkMixin作为直通模型，所以希望以某种方式避免它。

标签： pythondjangodjango-ormdjango-related-manager