I'm looking for a way or for suggestions on how to initialize lazy loaded collections in bulk.

For example, let's say I have a class like the following:



I have already loaded a list of Person objects via a query. Now that I have the Person objects, is there a way to initialize a collection of Person in bulk (e.g., I pass in a list of Person objects and say that I want the friendSet collection initialized - hibernate performs a single query with an outer join and populates all of the Person objects)? I see that I can iterate thru each one and call Hibernate.initialize but that will make a db call each time.

In Hibernate 2.1 you can set the batch-size attribute of <set>. Your Java code will look identical.

Thanks. That seems to be working but it is behaving oddly regarding the batching.

Is the batch-size setting stable in 2.1b6?

If I set the batch-size to 100, it loads in batches of 10. If I set the batch-size to 50 it loads the first two batches in batches of 7 and the rest one at a time.

My set mappings look like:

This is correct (and good) behavior.

Suppose I had 66 instances to load, and batch-size=50:

Batch 1: size 50
Batch 2: size 7
Batch 3: size 7
Batch 4: size 1
Batch 5: size 1


7 = sqrt(50), by the way.

This solution means I can pregenerate the SQL up front, without needed to generate 50 different statements - and it also might help to achieve efficient prepared statement caching.

P.S. I'm not convinced that 50 is a sensible batch size. I would think that 16 or 25 are at least large enough.

Hi Gavin,



I looked at Hibernate 2.1.1 and 2.1.2 - it seems to me that it behaves slightly different compared to what you've said:

Setting Batchsize to 50 leads to the following batch size pattern:
Batch 1: size 7!!
Batch2: size 7
.....
So that means to be able to fetch 50 I must set batch-size to 50^2
But unfortunatly hibernate decides to fall back to default batch-size = 1, when batch-size is set too large (I tried 121 - it works so I am able to batch fetch 11 instances, but 225 fails....

It's areal problem for me because we have some huge object graphs to load! Shall I submit it to JIRA as bug?

Cheers,

Manuel

Ok ok - I withdraw that :D

I took a look in the code - batch-size is a difficult area - it's very sensitiv - setting it too high can have a very counterproductive outcome...

I will look deeper into it - maybe that can solve my problems...

Cheers,

Manuel