[clarification]: Keyset pagination, what should happen when the order is not defined?

[otaviojava]

Specification

https://github.com/jakartaee/data/blob/main/spec/src/main/asciidoc/repository.asciidoc#restrictions-on-use-of-cursor-based-pagination

I need clarification on ...

At the specification, there is this point:

Sort criteria must be provided and should be minimal.

But what happens if the user does not inform any Sort element?

Using the same spec example:

@Repository
public interface Products extends CrudRepository<Product, Long> {
    CursoredPage<Product> findByNameLike(String namePattern, PageRequest<Product> pageRequest);
}

In this case, I will remove the Order method:

float priceMidpoint = 50.0f;
PageRequest<Product> pageRequest =
    //Order.by(_Product.price.asc(), _Product.id.asc()) removed, please, ignore if it will compile or not
PageRequest
             .pageSize(10)
             .afterKey(priceMidpoint, 0L);
CursoredPage<Product> moreExpensive =
        products.findByNameLike(pattern, pageRequest);

Additional information

No response

[njr-11]

PageRequest<Product> pageRequest =
    //Order.by(_Product.price.asc(), _Product.id.asc()) removed, please, ignore if it will compile or not
PageRequest
             .pageSize(10)
             .afterKey(priceMidpoint, 0L);
CursoredPage<Product> moreExpensive =
        products.findByNameLike(pattern, pageRequest);

The example you gave is a user error for two reasons.

One reason is that it violates the rule from the specification that you cited:

Sort criteria must be provided and should be minimal.

The second reason is there is also a requirement for the size of the sort criteria to exactly match the number of key components of the cursor. In your example, you have 2 key components supplied to afterKey but the size of the sort criteria is 0.

The example usage can be rejected on the basis of either of these.

[otaviojava]

Thanks, @njr-11; my question is, what exception should I throw?

• IllegalStateException
• UnsupportedOperationException
• DataException
• a Jakarta Data provider

The specification is not clear at this point.

[njr-11]

I would recommend IllegalArugmentException because the user has supplied a PageRequest argument that is not appropriate for cursor-based pagination -- it has no Sorts and its number of key components does not match the amount of sort criteria.

[gavinking]

I agree, that was my thought too.