datastore/query.go
func (q *Query) EventualConsistency() *Query {
	q = q.clone()
	q.eventual = true
	return q
}
func (q *Query) EventualConsistency() *Query {
	q = q.clone()
	q.eventual = true
	return q
}
// EventualConsistency returns a derivative query that returns eventually
// consistent results.
// It only has an effect on ancestor queries.