google cloud datastore - gae ndb query failing to find related records with key property -


i'm trying implement code won't let entity deleted if has related entities.

class father(ndb.model):     name = ndb.stringproperty(indexed=true)  class son(ndb.model):     name = ndb.stringproperty(indexed=true)     father = ndb.keyproperty(father)

this code:

father = father.get_by_id(long(keynumber)) if father:     father_key = father.key     if father_key:         sons = son.query(son.father==father_key).fetch()         number_of_sons = len(sons)         if number_of_sons == 0:             father_key.delete()

when runs, sons empty list [] although there related sons father.

why doesn't query work?

as @patrick costello suggests, using strongly-consistent query right way handle this:

class father(ndb.model):     name = ndb.stringproperty(indexed=true)  class son(ndb.model):     name = ndb.stringproperty(indexed=true)      @classmethod     def create(cls, name, father):         son = cls(name=name, parent=father)         son.put()

i recommend using count() operation:

father = father.get_by_id(long(keynumber)) if father:     father_key = father.key     if father_key:         sons_exist = son.query(ancestor=father_key).count(1)         if sons_exist == 0:             father_key.delete()

by counting 1, result of count(1) true/false (1/0) value.

not exact duplicate, this question similar.


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