How to use Google Cloud Datastore Statistics

Question

How can I use Google Cloud Datastore stats object (in Python ) to get the number of entities of one kind (i.e. Person) in my database satisfying a given constraint (i.e. age>20)?

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 (i.e. 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.