count() function

apostle · **Joined:** Mon Feb 22, 2010 2:07 pm **Posts:** 8

I am using ogm with mongodb on Glassfish v4.0.1.

Code:

@Entity
@Table(name = "blog_entry")
@NamedQueries({
        @NamedQuery(name = "blog_entry_list", query = "select be from BlogEntry be order by be.created"),
        @NamedQuery(name = "blog_entry_count", query = "select count(be) from BlogEntry be"),
})
public class BlogEntry extends AbstractEntity {
....
}

Code:

@Stateless
public class BlogEntryDaoBean extends AbstractDaoBean<BlogEntry> implements
      BlogEntryDao {
...

@Override
    public Long count() {
        Object result =  getEntityManager().createNamedQuery("blog_entry_count").getSingleResult();
        return (Long) result;
   }
}

when the blog_entry_count query is exequted, the result is of BlogEntry type. I would expect it to be a number in this case. Does ogm supports aggregate functions and count() in particular in HQL? Unfortunately I have not found any notion in the documentation. Thank you.
---------------------------
hibernate-ogm 4.1.0.Beta2, mongodb driver 2.11.3

apostle · **Joined:** Mon Feb 22, 2010 2:07 pm **Posts:** 8

It appeared I was reading the documentation for version 3 and in the documentation for v4.1(http://docs.jboss.org/hibernate/ogm/4.1/reference/en-US/html_single/) it is stated there is no support for the aggregation functions

Quote:

no join, aggregation, or other relational operations are implied

I would still like to ask if any support for at least count() function is planned? Thank you

Gunnar · **Joined:** Sat Jan 24, 2009 12:46 pm **Posts:** 388

Hi,

We don't yet support any JP-QL/HQL functions when executing queries on MongoDB. I think it's a common requirement in applications where one wants to page through a result set, so I've created https://hibernate.atlassian.net/browse/OGM-534. Maybe you would like to help out with implementing this?

--Gunnar

Gunnar · **Joined:** Sat Jan 24, 2009 12:46 pm **Posts:** 388

Btw. I'm planning to look into providing more powerful means of native queries for MongoDB (see https://hibernate.atlassian.net/browse/OGM-513; Currently only find() operations are possible). This would allow you to get the count like so:

Code:

@NamedNativeQuery(name = "blog_entry_count", query = "db.runCommand( { count: 'orders' } )"

Regarding the docs, the currently supported JP-QL constructs are listed in the reference guide here: https://docs.jboss.org/hibernate/ogm/4.1/reference/en-US/html_single/#ogm-mongodb-queries

--Gunnar

apostle · **Joined:** Mon Feb 22, 2010 2:07 pm **Posts:** 8

Gunnar, thank you for the answer.

Quote:

Maybe you would like to help out with implementing this?

Maybe I can try. I have checked out the source code and debugged it a little bit just to see how it works internally. Cannot say I already figured out the way to go it would take some time.. I have never contributed for any open source products, so if can give little inside about the process and/or give a link to a process description I would really appreciate it. Actually any help with understanding how it works would be great.

Pavel