Support usage of distinct on properties [DATACMNS-115]

[spring-projects-issues]

Thomas Hackel opened DATACMNS-115 and commented

Allow to use a method like:

List<String> findDistinctName();

SQL Equivalent:
select distinct(name) from foo;

Also additional where clause should work too:
List<String> findDistinctNameByLastName(String lastName);

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Issue Links:

• DATACMNS-89 Support for projections in repository query methods
  ("depends on")

5 votes, 7 watchers

[spring-projects-issues]

Mayur Soneta commented

Can someone please tell what version this would be implemented. Seems to me a basic one. Please update

[spring-projects-issues]

Oliver Drotbohm commented

You might wanna vote for the feature if it's urgent to you. You can work around the limitation by using the @Query annotation available from the store-specific modules. We actually need to fix DATACMNS-89 first. Beyond that, contributions are always welcome :)

[spring-projects-issues]

Mayur Soneta commented

I wrote a method for that, can you please do review on that.

public static List<String> findByFieldValue(String fieldName, String searchTerm, EntityManager em) {

    // Create CriteriaBuilder object
    CriteriaBuilder builder = em.getCriteriaBuilder();
    // ONly for String
    CriteriaQuery<String> q = builder.createQuery(String.class);

    // Currently only for ProjectCommonInfo domain
    Root<DomainClass> domainClass = q.from(DomainClass.class);

    // making distinct
    q.select(domainClass.<String>get(fieldName));
    q.distinct(true);

    q.where(builder.like(builder.lower(domainClass.<String>get(fieldName)),
            builder.parameter(String.class, "param")));

    TypedQuery<String> tq = em.createQuery(q);
    tq.setParameter("param", searchTerm.toLowerCase());
    return tq.getResultList();

}

[spring-projects-issues]

Jens Schauder commented

Sorry for the late answer.

Any PR should be based on master. If anybody needs feedback on implementation details, please provide code in a github repository. We can't really do a useful code review on a single detached method

[spring-projects-issues]

Jens Schauder commented

If I'm not mistaken, we currently ignore the name part between find and By. So this would actually change existing behavior. So it should go into a major release.
It probably also should consider the return type of the method, to ensure it can be converted to from the type of the referenced property