Hibernate reactive panache pagination with OneToMany entity

[beiertu-mms]

We're using hibernate-reactive-panache v3.7.1 with these two entities

@Entity
@Table(name = "owner")
@NamedQuery(name = "Owner.findById", query = "from Owner o left join fetch o._pets p where o.id = :id")
class Owner() {
    @OneToMany(
        cascade = [CascadeType.ALL],
        fetch = FetchType.LAZY,
        mappedBy = "owner",
        orphanRemoval = true
    )
    private val _pets = mutableListOf<Pet>()

    val pets get() = _pets.toList()

    fun addPet(pet: Pet) {
        if (_pets.contains(pet)) {
            throw IllegalArgumentException("The same pet can not be assigned to the same owner again!")
        }
        this._pets.add(pet)
    }
}

@Entity
@Table(name = "pet")
class Pet() {
    @ManyToOne(fetch = FetchType.LAZY, optional = false)
    @JoinColumn(name = "owner_id")
    @JsonIgnore // ignore to prevent infinite recursion when serialization
    lateinit var owner: Owner
}

and we want to use paging as described on the guide here.
But we're running into the issue with join fetch when trying to get the paging information (pageCount, count, etc.) beside the fetch result list.

This stackowerflow question suggests to use a countQuery but that's not possible with the NamedQuery at the moment.

So we tried to add a second NamedQuery without the join fetch part

@NamedQuery(name = "Owner.countById", query = "from Owner o where o.id = :id")

to mimic the countQuery and tried to use both of them together like this

val params = Parameters.with("id", id)
ownerRepository
    .find("#Owner.findById", params).page<Owner>(pageIndex, pageSize).list<Owner>()
    .flatMap { owners ->
        val query = repo.find("#Owner.countById", params).page<Owner>(pageIndex, pageSize)
        Uni.combine().all().unis(
            Uni.createFrom().item(query.hasPreviousPage()),
            query.hasNextPage(),
            query.pageCount(),
            query.count()
        ).with { hasPrev, hasNext, pageCount, count ->
            OwnerPage(result = owners, hasPrev = hasPrev, hasNext = hasNext, pageCount = pageCount, count = count)
    }
}

but this throws the error java.lang.IllegalStateException: Illegal pop() with non-matching JdbcValuesSourceProcessingState.

Do you have any suggestions on how this can be implemented?

[quarkus-bot[bot]]

/cc @DavideD (hibernate-reactive), @FroMage (panache), @gavinking (hibernate-reactive), @geoand (kotlin), @loicmathieu (panache)

[DavideD]

The problem is that, at the moment, operations using the session must run in a precise order. Basically, this means that you cannot use Uni.combine().all().unis(...).
It should work if you compose/chain the operations.

[beiertu-mms]

yes, chaining the operations work :)
Thank you @DavideD