google app engine - How to update one property for multiple NDB entities? -

i have ndb model class below:

class contest(ndb.model):     end_date = ndb.dateproperty(required=true, indexed=true)     ended = ndb.booleanproperty(required=false, indexed=true)     ... 

i have daily cron job mark contests passed end_date ended equal true. i've written following code it:

contests = contest.query() current_datetime = datetime.datetime.utcnow() today = datetime.date(current_datetime.year, current_datetime.month, current_datetime.day) contests = contests.filter(contest.end_date < today) contests = contests.filter(contest.ended == false) contests = contests.fetch(limit=10) contest in contests:     contest.ended = true ndb.put_multi(contests) 

but don't it, since have read entities update 1 value. there way modify read keys_only?

the object data overwrites existing entity. entire object sent datastore

https://cloud.google.com/datastore/docs/concepts/entities#datastore_updating_an_entity

so cannot send 1 field of entity, "remove" existing fields. more accurate - replace entity fields new version of entity have 1 field.

you have load entities want update, properties, not keys, set new value of property, , put database.