@ElementCollection(targetClass=String.class, fetch=FetchType.LAZY)
    @JoinTable(name="subject_attribute",joinColumns=@JoinColumn(name="attribute_id"))
    @Column(name="subject_id")
    @IndexColumn(name="sort_order")
    public List<String> getParentsIds() {
        return parentsIds;
    }

   public Object readFrom(ResultSet rs, CollectionPersister persister, CollectionAliases descriptor, Object owner)
   throws HibernateException, SQLException {
      Object element = persister.readElement( rs, owner, descriptor.getSuffixedElementAliases(), getSession() ) ;
      int index = ( (Integer) persister.readIndex( rs, descriptor.getSuffixedIndexAliases(), getSession() ) ).intValue();

      //pad with nulls from the current last element up to the new index
      for ( int i = list.size(); i<=index; i++) {
         list.add(i, null);
      }

      list.set(index, element);
      return element;
   }

//added block
   private ArrayList<Integer> ordering;
   public boolean endRead() {
      ordering = null;//release memory
      return super.endRead();
   }
//end added block

//modified method
public Object readFrom(ResultSet rs, CollectionPersister persister, CollectionAliases descriptor, Object owner) throws HibernateException, SQLException {
   Object element = persister.readElement( rs, owner, descriptor.getSuffixedElementAliases(), getSession() ) ;
   int index = ( (Integer) persister.readIndex( rs, descriptor.getSuffixedIndexAliases(), getSession() ) ).intValue();
   if (ordering==null) {
      ordering = new ArrayList<Integer>();
   }
   for (int i = 0; i < ordering.size(); i++) {
      if (ordering.get(i)>index) {
         //found
         list.add(i,element);
         ordering.add(i,index);
         return element;
      }
   }
   //new or the greatest
   list.add(element);
   ordering.add(index);
   return element;
}