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Using countDistinct()

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terralance

Post subject: Using countDistinct()

Posted: Fri Feb 26, 2010 5:20 am

Newbie

Joined: Fri Feb 26, 2010 5:08 am
Posts: 2

I recently upgraded to version 3.5.0-CR-2 but it seems Projections.count() and Projections.countDistinct() return the same result, for example:

Code:

criteria.setProjection(Projections.countDistinct("id"));

will get translated into:

Code:

select count(id) from ...

where I would expect count(distinct id). Is this a bug or is there something wrong with my understanding of the countDistinct() function?

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pb00067

Post subject: Re: Using countDistinct()

Posted: Fri Feb 26, 2010 5:40 am

Expert

Joined: Tue Jun 16, 2009 3:36 am
Posts: 990

I suggest to debug your application by putting breakpoints to

org.hibernate.criterion.CountProjection.java methods setDistinct() and toString()

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terralance

Post subject: Re: Using countDistinct()

Posted: Fri Feb 26, 2010 6:01 am

Newbie

Joined: Fri Feb 26, 2010 5:08 am
Posts: 2

Thanks for the quick reply, unfortunately it doesn't look really good. It is set on distinct, but it seems to put it in the wrong place:

Code:

distinct count(id)

But I think I found what changed from 3.3.2, there used to be a specific toSqlString() that put the distinct on the correct location:

Code:

public String toSqlString(Criteria criteria, int position, CriteriaQuery criteriaQuery) 
   throws HibernateException {
      StringBuffer buf = new StringBuffer();
      buf.append("count(");
      if (distinct) buf.append("distinct ");
      return buf.append( criteriaQuery.getColumn(criteria, propertyName) )
         .append(") as y")
         .append(position)
         .append('_')
         .toString();
   }

I don't know if the removal was intentional and distincts are treated somewhere else now.

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pb00067

Post subject: Re: Using countDistinct()

Posted: Fri Feb 26, 2010 6:38 am

Expert

Joined: Tue Jun 16, 2009 3:36 am
Posts: 990

Quote:

I don't know if the removal was intentional and distincts are treated somewhere else now.

For me it looks very like a unintentional bug, because

Code:

toSqlString(Criteria criteria, int position, CriteriaQuery criteriaQuery)

is now implemented in CountProjections superclass AggregateProjection solely
where the distinct property is not handled at all.

I suggest you to implement an appropriate junit-test-case and to open an issue on Hibernate Jira.
Such issue should be threated with absolutely priority, as this bug compromises 3.5 backward compatibility.

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