I have an entity called Item which has two properties, price and description. No collections or associations exist on this entity. I have a list of 1,000 identifiers for which I want to retrieve the instances. What is the fastest way to do this?

I tried setting the batch size in the mapping for Item to values ranging from 2 to 200, and also setting the hibernate.jdbc.batch_size property, and then calling Session.load(). LockMode.READ was used to ensure that the cache was being bypassed.

When looking at the SQL queries being generated, I see one query for each identifier, i.e. a thousand queries in order to retrieve the thousand instances. I was expecting to see some number close to (1000 / batch size). Also, none of the queries generated have an IN clause.

Is my understanding of how batch sizing works incorrect, i.e. does it only apply to collections? If not, what is the right approach to get this working?

Thanks,

-Kaare

The batch size you are updating is for jdbc-batch -


I think the one you want to update is -
hibernate.default_batch_fetch_size

Hmm, I added this setting so that I now have:



When I ask for a batch of 60 items I still get 60 SQL statements printed on the console. I verified that the properties are being picked up by the Settings class. The BatchingEntityLoader class is also being invoked.

This is strange. The approach I'm using is this: I compute the identifier for each of the entities being requested, call Session.get() on each of the identifiers, and the finally access the entitties (map instances). The SQL statements being printed are exactly the same (e.g. WHERE item0_.ITEM_ID=?) and do not have an IN clause (e.g. WHERE item0_.ITEM_ID IN (1,2,3).

Any ideas on how to home in on where the problem is?

Thanks,

-Kaare

Sorry, that should be Session.load(), not Session.get().

-Kaare

Are you previously running a query for hte identifiers?

I was doing something like this for paging before. is much better idea to use the built in paging functionality than getting ids.

Perhaps you can provide more info on what exactly you are trying to do...I don't think there is a way to do it as a batch if you are simply doing session.load on single entities. Hibernate doesn't know that you might do another session.load. You have to do some sort of collection get. Then the batch size properties will kick in