How do I use JPA to select the record with the closest date? - spring-data

Question

Let's say I have a collection of Rates that all inherit from an AbstractRate
#MappedSuperclass
#Inheritance(strategy = InheritanceType.SINGLE_TABLE)
#DiscriminatorColumn(name = "name")
#Table(name = "rates")
public abstract class AbstractRate {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
private String name;
#Column(precision = 13, scale = 4)
private BigDecimal value;
#OneToOne
private EffectiveDate effectiveDate;
...
}
And, that all have an EffectiveDate:
#Entity
public class EffectiveDate {
#Id
private LocalDateTime date;
...
}
(I acknowledge that a separate date object is a little over-kill for this model, but it's allowing me to bind multiple rates and other figures in the database.)
Now, I'd like to get a specific Rate, say SalaryRate, that is effective as of a certain date. I can do something like
salaryRateRepository.findByEffectivedate(
effectiveDateRepository.findTopByDateLessThanEqualOrderByDateDesc(sampleDate)
);
This should effectively give me a the MAX(date) and its matching Rate. Is this the right way to query these things? Some posts suggest
As an additional option, I have Querydsl setup and the repositories extend QuerydslPredicateExecutor. However, I'm not really familiar with how Querydsl's syntax works.

Answer 1

I think all is OK with findTopByDateLessThanEqualOrderByDateDesc(sampleDate).
Another variants should be:
#Query(value = "select * from effective_date ed where ed.date <= ?1 order by ed.date desc limit 1", nativeQuery = true)
EffectiveDate findEffectiveDate(LocalDateTime dateTime);
or
Predicate p = QEffectiveDate.effectiveDate.date.loe(sampleDate);
Pageable page = new PageRequest(0, 1, new Sort(Sort.Direction.DESC, "date"));
//...
EffectiveDate effectiveDate = effectiveDateRepository.findAll(p, page).getContent().stream().findFirst().orElse(null);
(not tested...)