Don't use findAll(Pageable pageable)

[simasch]

When using Page<T> findAll(Pageable pageable) Spring Data will execute the select plus the count query for every call.

This can be very inefficient and in the case of a DataProvider with paging and sorting simply superfluous.

It would be better to add a custom method to the Repository like:

List<T> findBy(Pageable pageable)

to avoid the unnecessary count query.

[Artur-]

Sounds like a good idea but although

    List<SamplePerson> findBy(Pageable pageable);

works fine in a repository it seems like

    List<SamplePerson> findBy(Specification<SamplePerson> filter, Pageable pageable);

does not: "org.springframework.dao.InvalidDataAccessApiUsageException: At least 1 parameter(s) provided but only 0 parameter(s) present in query"

[simasch]

The problem maybe because the JpaSpecificationExecutor does only define these methods:

public interface JpaSpecificationExecutor<T> {
    Optional<T> findOne(@Nullable Specification<T> spec);

    List<T> findAll(@Nullable Specification<T> spec);

    Page<T> findAll(@Nullable Specification<T> spec, Pageable pageable);

    List<T> findAll(@Nullable Specification<T> spec, Sort sort);

    long count(@Nullable Specification<T> spec);

    boolean exists(Specification<T> spec);

    long delete(Specification<T> spec);

    <S extends T, R> R findBy(Specification<T> spec, Function<FluentQuery.FetchableFluentQuery<S>, R> queryFunction);
}

[Artur-]

I think the problem is that you cannot mix By and Specification so the hack of using findBy cannot be used. It is also not possible to use findAll with a different return type.. So I'm not sure how create a method that would accept both Specification and Pageable but not return Page

[simasch]

Yeah, that's indeed a problem!

[simasch]

I don't understand why PagingAndSortingRepository does not support a findAll that returns a Slice or just a List

[Artur-]

Let's see if there are any comments in spring-projects/spring-data-jpa#2762