排序查询

Question

下面的这组查询将一组配置文件连接在一起，以返回到一个网站

我想用它们做一个查询，因为我想对整个概要文件集合使用order函数

# Get all users for who 'currentUser' is an assistant for.
users = Users.query(Users.assistant.IN(currentUser)).fetch()

# Get all profiles that belong to those users and have not been deleted.
for user in users:
    profiles = profiles + Profiles.query(
            ndb.AND(
            Profiles.user == user.username,
            Profiles.deleted == False
        )
    ).order(Profiles.history).fetch() # Order all profiles by timestamp

Answer 1

在某种程度上，你所寻找的将相当于：

# get the list of usernames obtained above
usernames = [user.username for user in users]

profiles = Profiles.query(ndb.AND(Profiles.user.IN(usernames),
                                  Profiles.deleted == False))
                         .order(Profiles.history).fetch()

但是，如果usernames包含许多元素（显然超过10个左右），则会出现性能问题，请参见Does the NDB membership query ("IN" operation) performance degrade with lots of possible values?