[OPENJPA-2553] JPQL AVG returns Int instead of Double wrt. @ElementCollection

• Type: Bug
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Affects Version/s: 2.4.0
• Component/s: query
• Environment: Apache Tomee plus 1.7.1, openjpa-2.4.0-nonfinal-1598334.jar, hsqldb-2.3.2, H2DB-2014-12-19
• Assignee: Unassigned
• Reporter: Apache Fan
• Created: 28/Dec/14 22:54
• Updated: 02/Jan/15 21:25

Description

The following JPQL query is executed to get the average of values stored in a Map.

@NamedQueries({
  @NamedQuery(name = "selectFromMap", 
      query = "SELECT new dao.entity.AggregationResultHolder(AVG(p), KEY(p)) FROM Evaluation e, IN (e.scores) p "
              + "WHERE e.subject.id=:subjectId GROUP BY KEY(p)")
})

Entity:

public class Evaluation {
...
  @ElementCollection
  @MapKeyColumn(name = "criteria_id") 
  @Column(name = "criteria_score")
  private Map<Criteria, Integer> scores = new HashMap<Criteria, Integer>();
...
}

• Expected behaviour: the AVG value is returned as Double (according to http://openjpa.apache.org/builds/2.3.0/apache-openjpa/docs/jpa_langref.html#jpa_langref_aggregates )
• Experienced behaviour: the average is returned as Integer (and exception is thrown if the AggregationResultHolder class' constructor is not Integer-based). Unfortunately this way the fraction digits are lost.

Workaround: after modifying the Map to <Criteria, Double> in the entity, the query returns Doubles for the average (however the fraction digits are still lost in case of HSQLDB). Obviously it is a sub-optimal solution, as the schema has to be changed.