SELECT ID(entityvar) only returns part of IdClass

[Riva-Tholoor-Philip]

The following JPQL,

SELECT ID(THIS) FROM City WHERE (name=?1) ORDER BY population DESC

is used on an entity,

@Entity
@IdClass(CityId.class)
public class City {
    @Id
    public String name;
    public int population;
    @Id
    public String stateName;
    ...
}

with an IdClass

public record CityId(String name, String state) implements Serializable

The result ought to be a list of CityId.
Instead, it returns a list of String where the values are the stateName entity attribute, which is only one of the two components of the ID.

It looks like the same error occurs with the ID() function regardless of whether the entity identification variable is THIS or something else. I tried with SELECT ID(o) FROM City o and saw the same result.

It should be noted that section 4.7.11 of the Jakarta Persistence 3.2 specification states that, "A persistence provider is not required to support the use of the ID function for entities with composite primary keys." That means EclipseLink would have the option of raising an error and declaring the ID() function to be unsupported when IdClass is used. However, that is not what is happening here either. It is clearly trying to support the function, but returning the wrong value--only part of the composite primary key rather than the IdClass value that is the entire primary key.

[Riva-Tholoor-Philip]

I am looking into this issue

[lukasj]

visit(IdExpression) should probably be updated; one may want to be checking also mapping.derivesId()

[lukasj]

probably a problem on line 66 there

[Riva-Tholoor-Philip]

Thanks Lukas. Will look into this

[rfelcman]

A few hints about this issue:

• org.eclipse.persistence.internal.jpa.jpql.JPQLFunctionsAbstractBuilder#visit(org.eclipse.persistence.jpa.jpql.parser.IdExpression) primaryKeyFields variable is list so instead of String idAttributeName = this.getIdAttributeNameByField(descriptor.getMappings(), (DatabaseField)primaryKeyFields.get(0)); there should be some loop into something like List<String> idAttributeNames.
• useful info about target @IdClass(....) should be in descriptor.cmpPolicy
• it should leads into org.eclipse.persistence.internal.descriptors.ObjectBuilder#buildNewRecordInstance call instead of simple String