joinedload() vs join()

[mgoz...@starfishstorage.com]

Hi

I have a question about the difference between .join() and .options(joinedload()).

I'm using example from http://docs.sqlalchemy.org/en/rel_1_0/orm/extensions/hybrid.html#working-with-relationships (the one with SavingsAccount and User)
The doc shows SQL for

Session().query(User, User.balance).join(User.accounts).filter(User.balance > 5000)

which is

SELECT "user".id AS user_id, "user".name AS user_name, account.balance AS account_balance
FROM "user" JOIN account ON "user".id = account.user_id
WHERE account.balance > :balance_1

if I change the Python code to

Session().query(User, User.balance).options(joinedload(User.accounts)).filter(User.balance > 5000))

it generates different SQL, which I believe does a cartesian join:

SELECT "user".id AS user_id, "user".name AS user_name, account.balance AS account_balance, account_1.id AS account_1_id, account_1.user_id AS account_1_user_id, account_1.balance AS account_1_balance

FROM account, "user" LEFT OUTER JOIN account AS account_1 ON "user".id = account_1.user_id

WHERE account.balance > :balance_1

Is there something I'm missing?

[Mike Bayer]

joinedload() only refers to collections that are fully loaded on User
and aren't part of what you can manipulate in the query. Take a look at
http://docs.sqlalchemy.org/en/latest/orm/loading_relationships.html#the-zen-of-eager-loading
.





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[Marcin Gozdalik]

Thanks for the link. It seems I missed that.

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