django – 如何在基于过滤器的ManyToMany关系中删除多个对象?
发布时间:2020-12-16 23:02:19 所属栏目:Python 来源:网络整理
导读:给出这两个模型: class Item(models.Model): timestamp = models.DateTimeField()class Source(models.Model): items = models.ManyToManyField(Item,related_name="sources") 我可以在给定的时间之前使用以下内容找到所有的Source的项目: source.items.fi
给出这两个模型:
class Item(models.Model): timestamp = models.DateTimeField() class Source(models.Model): items = models.ManyToManyField(Item,related_name="sources") 我可以在给定的时间之前使用以下内容找到所有的Source的项目: source.items.filter(timestamp__lte=some_datetime) 如何有效地删除与该查询匹配的所有项目?我想我可以尝试这样的事情: items_to_remove = list(source.items.filter(timestamp__lte=some_datetime)) source.items.remove(*items_to_remove) 但这似乎不好 请注意,我不想删除这些项目,因为它们也可能属于其他来源.我只想删除他们与具体来源的关系. 解决方法
我认为你的钱是正确的,除非你不需要转换成清单.
source.items.remove(*source.items.filter(*args)) remove / add方法如下所示 remove(self,*objs) add(self,*objs) 和文档http://www.djangoproject.com/documentation/models/many_to_many/ >>> a2.publications.add(p1,p3) 多一点挖掘,remove函数逐个迭代* obj,检查它是否是有效的模型,否则使用值作为PK,然后删除与pk__in的项目,所以我会说是的,最好的方法是首先查询您的m2m表,以删除对象,然后将这些对象传递给m2m管理器. # django.db.models.related.py def _remove_items(self,source_field_name,target_field_name,*objs): # source_col_name: the PK colname in join_table for the source object # target_col_name: the PK colname in join_table for the target object # *objs - objects to remove # If there aren't any objects,there is nothing to do. if objs: # Check that all the objects are of the right type old_ids = set() for obj in objs: if isinstance(obj,self.model): old_ids.add(obj.pk) else: old_ids.add(obj) if self.reverse or source_field_name == self.source_field_name: # Don't send the signal when we are deleting the # duplicate data row for symmetrical reverse entries. signals.m2m_changed.send(sender=rel.through,action="pre_remove",instance=self.instance,reverse=self.reverse,model=self.model,pk_set=old_ids) # Remove the specified objects from the join table db = router.db_for_write(self.through.__class__,instance=self.instance) self.through._default_manager.using(db).filter(**{ source_field_name: self._pk_val,'%s__in' % target_field_name: old_ids }).delete() if self.reverse or source_field_name == self.source_field_name: # Don't send the signal when we are deleting the # duplicate data row for symmetrical reverse entries. signals.m2m_changed.send(sender=rel.through,action="post_remove",pk_set=old_ids) (编辑:李大同) 【声明】本站内容均来自网络,其相关言论仅代表作者个人观点,不代表本站立场。若无意侵犯到您的权利,请及时与联系站长删除相关内容! |
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