我一直认为在Django中链接多个filter()调用总是与在单个调用中收集它们相同。
# Equivalent
Model.objects.filter(foo=1).filter(bar=2)
Model.objects.filter(foo=1,bar=2)
但是我在代码中遇到了一个复杂的查询集,情况并非如此
class Inventory(models.Model):
book = models.ForeignKey(Book)
class Profile(models.Model):
user = models.OneToOneField(auth.models.User)
vacation = models.BooleanField()
country = models.CharField(max_length=30)
# Not Equivalent!
Book.objects.filter(inventory__user__profile__vacation=False).filter(inventory__user__profile__country='BR')
Book.objects.filter(inventory__user__profile__vacation=False, inventory__user__profile__country='BR')
生成的SQL是
SELECT "library_book"."id", "library_book"."asin", "library_book"."added", "library_book"."updated" FROM "library_book" INNER JOIN "library_inventory" ON ("library_book"."id" = "library_inventory"."book_id") INNER JOIN "auth_user" ON ("library_inventory"."user_id" = "auth_user"."id") INNER JOIN "library_profile" ON ("auth_user"."id" = "library_profile"."user_id") INNER JOIN "library_inventory" T5 ON ("library_book"."id" = T5."book_id") INNER JOIN "auth_user" T6 ON (T5."user_id" = T6."id") INNER JOIN "library_profile" T7 ON (T6."id" = T7."user_id") WHERE ("library_profile"."vacation" = False AND T7."country" = BR )
SELECT "library_book"."id", "library_book"."asin", "library_book"."added", "library_book"."updated" FROM "library_book" INNER JOIN "library_inventory" ON ("library_book"."id" = "library_inventory"."book_id") INNER JOIN "auth_user" ON ("library_inventory"."user_id" = "auth_user"."id") INNER JOIN "library_profile" ON ("auth_user"."id" = "library_profile"."user_id") WHERE ("library_profile"."vacation" = False AND "library_profile"."country" = BR )
具有链接filter()
调用的第一个查询集两次连接库存模型,从而有效地在两个条件之间创建了一个OR,而第二个查询集将这两个条件与在一起。我期望第一个查询也可以同时满足这两个条件。这是预期的行为,还是Django中的错误?
相关问题的答案在Django中使用“ .filter()。filter()。filter()...”有不利之处吗?似乎表明两个查询集应该等效。