Here is my situation: I have two Datastore kind, I need to create a python query for all Data that don't are present in Kind B. In the sample those are: Data 3 and Data 4.
The constraint here is that i need to filter for elements in KindA which have a key that is different from specific KindB property.
| Kind A | Kind B |
|---|---|
| Data 1 | Data 1 |
| Data 2 | Data 2 |
| Data 3 | |
| Data 4 | |
| Data 5 | Data 5 |
According to documentation, I can create a query in this way:
query = Account.query(Account.userid == 42)
I've tried this:
myquery = KindA.query(KindA.key.id() != KindB.documentId)
But it throws:
AttributeError: 'ModelKey' object has no attribute 'id'
I've tried following this stack overflow question: but it seems infeasible because the number of element in kindB is dynamic, and I can't list them all.
Written in english my query would be: filter KindA elements keys that are NOT IN KindB documentId.
Could you help?
Try this
# keys_only=True means Return only the keys which is faster
kindB_Ids = [ a.id() for a in KindB.query().fetch(keys_only=True) ]
kindA_Ids = [ a.id() for a in KindA.query().fetch(keys_only=True) ]
# This gives you rows in KindA whose ids are not in KindB
diff = [ ndb.Key(KindA, a) for a in KindA_Ids if a not in kindB_Ids]