Hibernate Reactive Panache joining relations

[agreedSkiing]

Hi.
So we are running into a bit of a problem and we don't know what is best to do. We want to use Hibernate Reactive with Panache and the repository pattern to query the @manytoone relation to its @onetomany relation and the other way around depending on which rest endpoint/service is called, but we are running into a problem when we try to load the relation with HQL with a query similar to

select distinct o from Order o left join fetch o.lineItems

Simplified Hibernate Reactive with Panache#simplified-queries.

Are we doing it wrong? Is there an another way like doing it “programmatically” (don’t know if it is the right term) or with a simple query? What is the best practice to do this with reactive hibernate and Panache?

[quarkus-bot[bot]]

/cc @DavideD, @FroMage, @Sanne, @gavinking, @loicmathieu

[DavideD]

but we are running into a problem when we try to load the relation with HQL

Hi, what kind of problem?

[agreedSkiing]

Did notice that but can't find another way to do it programmatically like the code i always like to look at https://learn.microsoft.com/en-us/ef/ef6/querying/related-data#eagerly-loading, but wait it might be possible with a criteria query if we use the plain reactive hibernate instead of panache

[DavideD]

Ah, wait, are you saying that it only works with Mutiny.fetch and doesn't when you use fetch join in a HQL?

This sounds like a bug in Hibernate Reactive. If that's the case, can you create an issue on the Hibernate Reactive issue tracker:
https://github.com/hibernate/hibernate-reactive/issues

I'm a bit busy now but I will get back to it.

Also now we are thinking why use Panache when most of us are used to Hibernate and JPQL and why not just use Reactive Hibernate which is a new learning experience in itself.

Panache is an API on top of Hibernate Reactive. It simplify some operations using the entities by providing some convenient methods to run the most common operations.
It's not a strict requirement and you can inject the Mutiny.SessionFactory, if you prefer. Or, you can access the Mutiny.Session via Panache.getSession().

That said, this error doesn't seem related to Panache and I think it would happen anyway .

[agreedSkiing]

@DavideD do you have any tips to join a manytomany relation in a .getResultList()/.list() with call or chain?

[agreedSkiing]

Ah, wait, are you saying that it only works with Mutiny.fetch and doesn't when you use fetch join in a HQL?

This sounds like a bug in Hibernate Reactive. If that's the case, can you create an issue on the Hibernate Reactive issue tracker: https://github.com/hibernate/hibernate-reactive/issues

I'm a bit busy now but I will get back to it.

Also now we are thinking why use Panache when most of us are used to Hibernate and JPQL and why not just use Reactive Hibernate which is a new learning experience in itself.

Panache is an API on top of Hibernate Reactive. It simplify some operations using the entities by providing some convenient methods to run the most common operations. It's not a strict requirement and you can inject the Mutiny.SessionFactory, if you prefer. Or, you can access the Mutiny.Session via Panache.getSession().

That said, this error doesn't seem related to Panache and I think it would happen anyway .

No no, fetch join works perfectly fine our problem was a bad json mapping that made our child object call the parent object which had no transaction context when trying to load the set of children.

[DavideD]

@DavideD do you have any tips to join a manytomany relation in a .getResultList()/.list() with call or chain?

Not sure, it depends on the specific use case.