如何使用Google Cloud Datastore统计信息

Question

如何使用Google Cloud Datastore stats对象（在Python中）来获取数据库中满足给定约束（例如age> 20）的一种实体（即Person）的数量？

Answer 1

Query objects have a nice count method which you could use:

qry = Person.query(Person.age > 20)
n_people_older_than_20 = qry.count()

Here I assume you're using the ndb queries (ie Person is an ndb.Model subclass). I'm sure that there's an equivalent for the older db interface as well ...

Answer 2

You can't, that's not what it's for at all. It's only for very broad-grained statistics about the number of each types in the datastore. It'll give you a rough estimate of how many Person objects there are in total, that's all.