批量删除多对多字段 django ORM

Question

Hii i have 1 model named College and in the model i have document_files field which is Many2ManyField now when i delete College objects i have to delete document_files also

Below is my code and Model,

    college_datas = College.objects.filter(id__in=[1,2])
            if college_datas.exists():
                for college in college_datas:
                    college.document_files.all().delete()
                    college.delete()

class College(models.Model):
    name = models.CharField(null=True, blank=True)
    document_files = models.ManyToManyField(CollegeDocuments, through='CollegeDocumentsThrough')

      class Meta:
        verbose_name_plural = "College"

Here i am using for loop which i think its time consuming so i am finding efficent way to bulk delete the college queryset and also removes the associated Many2ManyField data also.

Answer 1

First a clarifying question: Are you sure you want to use a ManyToManyField field here? This allows several colleges to "own" the same document. Is that intentional? In that case, you probably need some logic to make sure you only delete the documents that are not also related to other colleges.

If, on the other hand, a document should only belong to a single college, I would remove the document_files on the College model and instead add a ForeignKey field called college on the CollegeDocuments model. If you then set on_delete=CASCADE on that field, the related documents will automatically be deleted along with the college. Have a look at the documentation for on_delete .

If you want to stick to the ManyToManyField version and don't care about multiple colleges owning the same documents, you can (from the top of my head) do something along the lines of:

CollegeDocuments.objects.filter(college_set__in=college_datas).delete()

If you don't intend to delete the documents, but only disassociate them from the colleges you are deleting, you may want to use clear() . This still requires you to loop over the colleges, though. To do it in bulk, you can (again, from the top of my head), do something like:

CollegeDocumentsThrough.objects.filter(college__in=college_datas).delete()