Hibernate Query Language (HQL) - Queries for lazy/no-lazy loading

Question

I have a structure like this:

A contains collection of B (mapped as not-lazy)
B contains collection of C (mapped as not-lazy)

I'd like to make a query, that retrieves A objects, that contain B objects without the C objects within them. Is that possible? The other way around will work for me too (if B-C relation is mapped lazy and the query retrieves A, containing B and C).

Thanks!

Possible duplicate of Hibernate: Overriding mapping's EAGER in HQL? — davidwebster48
– davidwebster48, Commented Oct 21, 2015 at 1:59

JB Nizet · Accepted Answer · 2014-06-30 11:44:08Z

9

No, it's not possible. Since you marked the association itself as eagerly-loaded, Hibernate will always load this association eagerly.

If you mark the association as lazy (the default for toMany associations), then you have th option of eagerly fetching them in a query, using a join fetch:

select a from A a left join fetch a.bs b left join fetch b.cs

Note that this will not work if both of the collections are bags (i.e. Lists without index column).

edited Jun 30, 2014 at 11:44

answered May 14, 2012 at 13:09

JB Nizet

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4 Comments

Mooncrosser Over a year ago

Hello, thanks for the answer. I found this topic too, the answer is the same: stackoverflow.com/questions/3516873/… But I'm having some troubles making it work fine- it multiplies the "A" many times. Most likely my mistake.

Mooncrosser Over a year ago

Solved it, "distinct" is needed to make it work properly (I'm not an expert and I have no idea what's the difference). I'll mark this as correct answer, but it will be nice if you edit it or tell me where the difference is :)

JB Nizet Over a year ago

Without distinct, Hibernate returns 1 result per row of the JDBC resultset. This means that if you just have one A with 2 Bs, and each B has 2 Cs, the query will return 4 rows, and the list will contain 4 times the same instance of A. The distinct keyword makes Hibernate remove duplicates from the list.

Mooncrosser Over a year ago

Thanks you very much, after a day of banging my head in the wall, I've solved my issues ^^

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