CODEWITHSUNDEEP
pythongoogle-app-engineapp-engine-ndb
Alex Chan
Alex Chan

Reputation: 297

Google App Engine NDB keyproperty counter

I have a model for user to store their bookmarks. What is the best way to get the total number of bookmarks, should I create a field to store the number of total or aggregrate it when user retrieve the data ?

class UserBookMarks(Model):
    class Meta:
        behaviors = (searchable.Searchable,)
        search_exclude=('created')

    user= ndb.KeyProperty(kind=User, repeated=False)
    items = ndb.KeyProperty(kind=ItemList, repeated=True)
    created = ndb.DateTimeProperty(auto_now_add=True)

Upvotes: 0

Views: 364

Answers (1)

Martin Berends
Martin Berends

Reputation: 4178

Counting or aggregating in the Datastore is inefficient. Therefore create a field to store the total. If a counter needs to be updated more than a few times per second (unlikely with user bookmarks) you would need to resort to sharded counters.

Upvotes: 2

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