Grails createCriteria parent with last child

Question

How can I read only the lastChild along with parentObject

Parent {
  hasMany[children: Child]
}

here is my code

Parent.withCriteria() {
        eq("active", true)
        children {
            order("dateCreated", "desc")
            maxResults(1)
        }
    }

But not working. How can I read Parent with last updated child

Answer 1

hasMany in GORM/Hibernate does NOT have a filter semantics and always returns all referenced objects.

In a straight-forwad case you have to fire 2 queries: to find all Parents and to find all last updated children.

Another option would be to reverse the search logic: look for children 1st, group them by lastUpdated and then pull their parents. Of course, you must have a back-ref from Child to Parent:

class Child {
  static belongsTo = [ parent:Parent ]
}

Then the query could look something like:

Child.withCriteria{
  projections{
    groupProperty 'id'
    max 'lastUpdated'
  }
  parent{
    eq "active", true
  }
}