Why is this datastore querying by key returning None?

Question

1) When I perform this query:

contract_record = Contract(book_number = 42, initial_page = 420, final_page = 442)
contract_record.put()
contract_key = contract_record.key()
contract = db.GqlQuery("SELECT * FROM Contract WHERE __key__ = KEY('Contract', '$[contract_key]')").get()

The result is None. Why?

2) How to make this query not by the key, but the key_id? (something like this:

contract_id = contract_record.key().id()
contract = db.GqlQuery("SELECT * FROM Contract WHERE __key__ = KEY('Contract', '$[contract_id]')").get()

Thanks for any help!

Daniel Roseman · Accepted Answer · 2012-07-09T14:13:09.067

6

What is '$[contract_key]' supposed to be? Are you trying to do some sort of string substitution here? That really isn't how it works. Perhaps you mean to use the %s operator?

In any case, I don't really understand why you insist on doing queries via GQL. The way to get an object by its key is directly with get:

contract = db.get(contract_key)

and for the key ID:

contract = Contract.get_by_id(id)

edited Jul 09 '12 at 14:13

answered Jul 09 '12 at 13:50

Daniel Roseman

588,541
66
880
895

Thanks, @Daniel, I think only now I fully understand your previous advice (on how to get an datastore object by its key). Really thanks! – craftApprentice Jul 09 '12 at 15:47

score 1 · Answer 2 · answered Jul 09 '12 at 13:50

1

Maybe this is not the answer you are looking for, but you could try this:

contract_record = Contract(book_number = 42, initial_page = 420, final_page = 442)
contract_record.put()
contract_key = contract_record.key()
contract = db.get(contract_key)

answered Jul 09 '12 at 13:50

Lucas

919
4
15
32

Why is this datastore querying by key returning None?

2 Answers2