Django - 如何過濾ManyToMany模型對象？

Question

我有以下模型，通過外鍵和ManyToMany關係鏈接。

from django.db import models 
from django.contrib.auth.models import User 


class AssetMetadata(models.Model): 

    id = models.DecimalField(6).auto_creation_counter 
    material_id = models.CharField(max_length=256, blank=True) 
    series_title = models.CharField(max_length=256, blank=True) 
    season_title = models.CharField(max_length=256, blank=True) 
    season_number = models.IntegerField(default=0) 
    episode_title = models.CharField(max_length=256, blank=True) 
    episode_number = models.IntegerField(default=0) 
    synopsis = models.TextField(max_length=1024, blank=True) 
    ratings = models.CharField(max_length=256, blank=True) 

    def __str__(self): 
     return self.material_id 

class Batch(models.Model): 
    material_id = models.ManyToManyField(AssetMetadata) 
    user = models.ForeignKey(User, unique=True) 

    def __str__(self): 
     return 'Batch_' + str(self.pk) + '_' + self.user.username 

我可以看到，這工作，模型已經創建和關係工作，如你所期望的。從控制檯輸出中可以看到：

>>> from asset_db.models import Batch 
>>> Batch.objects.values() 
<QuerySet [{'user_id': 1, 'id': 1}, {'user_id': 3, 'id': 2}]> 

當我遷移模型時，它創建了下列表格（添加了以便您可以看到關係）。

asset_db_batch：

id | user_id 
____________ 
1 | 1 
2 | 3 

asset_db_batch_material_id：

id | batch_id | assetmetadata_id 
______|_____________|________________ 
1  |  1  |  1 
2  |  1  |  2 
3  |  1  |  6 
4  |  1  |  8 
5  |  1  |  4 
6  |  2  |  8 
7  |  2  |  2 
8  |  2  |  4 
9  |  2  |  7 

我的問題是我怎麼篩選Batch對象返回關聯到batch_id的項目？基本上，我如何在Django重新創建SQL查詢：

SELECT * FROM asset_db_batch_material_id 
    INNER JOIN asset_db_batch 
    ON asset_db_batch_material_id.batch_id = asset_db_batch.id 
    INNER JOIN asset_db_assetmetadata 
    ON asset_db_batch_material_id.assetmetadata_id = asset_db_assetmetadata.id 
WHERE user_id = 1 

Answer 1

類似於你如何與ForeignKey的

AssetMetadata.objects.filter(batch__user__id=1)