Repository returns PageImpl and executes count query when using Slice as return type [DATAJPA-1464]

Martin Möller opened DATAJPA-1464 and commented

public interface JavaUserRepositoryWithImplicitQuery extends Repository<User, Long> { 
    Slice<User> findAll(Pageable pageable); 
}

This repository returns at runtime a PageImpl and a count query is run against the db. As far as I understand Slice and Page, this should not happen.

The linked reproducer (branch is called slice) has tests that check for SliceImpl. Relevant is only the count query and not the implementation of Slice but they seem to be related. Logging is activated where the count query can be observed

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Affects: 2.1.2 (Lovelace SR2)

Reference URL: https://bitbucket.org/martinmo/spring-data-jpa-demo/src/4e2605ebfbaad16d973b6dbdc14b6d066b3a7fec/?at=slice

[odrotbohm]

That said, I can see why this is not immediately obvious that a call to the method would be executed that way. However, changing that would cause significant rework to the internal routing of calls, and I am not quite sure that I currently oversee the side effects of not routing the method call through the actual implementation but essentially executing a derived query for it. I’ll take this to the team for discussion.

Thanks for digging this up, though! 🙃

[odrotbohm]

You actually are, as in fact the JPA implementation of CrudRepository, SimpleJpaRepository implements PagingAndSortingRepository in preparation of our users declaring PASR as repository super type. Page<T> findAll(Pageable) is not a query method, and thus the optimization by using the different query method return type does not work. That’s what I am trying to say.