Google app engine: Poor Performance with JDO + Datastore
- by Bosh
I have a simple data model that includes
USERS: store basic information (key, name, phone # etc)
RELATIONS: describe, e.g. a friendship between two users (supplying a relationship_type + two user keys)
I'm getting very poor performance, for instance, if I try to print the first names of all of a user's friends. Say the user has 500 friends: I can fetch the list of friend user_ids very easily in a single query. But then, to pull out first names, I have to do 500 back-and-forth trips to the Datastore, each of which seems to take on the order of 30 ms. If this were SQL, I'd just do a JOIN and get the answer out fast.
I understand there are rudimentary facilities for performing joins across un-owned relations in a relaxed implementation of JDO (as described at http://gae-java-persistence.blogspot.com) but they sound experimental and non-standard (e.g. my code won't work in any other JDO implementation). Is this really my best bet?
Otherwise, how do people extract satisfactory performance from JDO/Datastore in this kind of (very common) situation?
-Bosh
