Failed JPASubQuery with count() in projection (Causes parse error in OpenJPA)

[Mats]

Hi,

I tried to get the following (stripped down) query to work:

JPAQuery query = new JPAQuery(logEntityManager);
QMessageLog messageLog = QMessageLog.messageLog;
QMessageLog otherMessageLog = new QMessageLog("otherMessageLog");

List<MessageLogProjection> messageLogResult = query.
  from(messageLog).
  where(filter).
  list(
    new QMessageLogProjection(
      messageLog,
      new JPASubQuery().from(otherMessageLog).where(otherMessageLog.originalMessageNumber.eq(messageLog.messageNumber)).count())
    );

@Immutable
public class MessageLogProjection {
  ...
  @QueryProjection
  public MessageLogProjection(MessageLog messageLog, Long newCount) {
  ...
  }
}

but it causes an error in OpenJPA:

org.apache.openjpa.persistence.ArgumentException: An error occurred while parsing the query filter "select messageLog_, (select count(otherMessageLog) from MessageLog otherMessageLog_ where otherMessageLog_.originalMessageNumber = messageLog_.messageNumber) from MessageLog messageLog_". Error message: Attempt to query field "otherMessageLog" from non-entity variable "otherMessageLog". Perhaps you forgot to prefix the path in question with an identification variable from your FROM clause?

To me it seems that the entity name in count(otherMessageLog) is missing an underscore and should have been count(otherMessageLog_) instead or am I missing something?

If I replace count() in the sub query with eg unique(otherMessageLog.id) (which also results in a Long) the query works.

I'm new to QueryDSL and unsure about which query constructions that is supported... 

Is it a bug or am I doing something wrong? Can it be worked around?

Thanks!

/Mats

[timowest]

Hi.

Could you create an issue for it on GitHub?

Timo

[Mats]

Sorry for the delay, I've created an issue #1329 now.

By the way, thanks a lot for an excellent framework. It's way nicer to work with than anything else I've tried in Java!

Thanks,

/Mats

[timowest]

Hi Mats.

Thanks for your kind words!

Timo