Is there an efficient mechanism for querying by the number of items in a repeated property in NDB?
I'd like to do something like:
Class.query(class.repeated_property.count == 2)
but of course this doesn't work.
Specifically, you can use ComputedProperty to automatically store the count, eg
class X(ndb.Model):
prop = ndb.StringProperty(repeated=True)
prop_count = ndb.ComputedProperty(lambda e: len(e.prop))
X.query(X.prop_count == 2)
在GQL中没有len查询语义,您需要具有列表长度的sperate属性并对其进行查询。
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