# Avoid unnecessary work

DON'T: In the example, below, the call to listSize() is unnecessary. In most cases, you shouldn't need to write something to loop over a collection:

    			if(query.listSize() > 0) {
    				while (iter.next()) { .... }
    			}

The call to `listSize()` will make an unnecessary call to "select count(*)". Let the iterator do the work. Avoid the extra call to the database.

Parent topic: Object-Relational Mapping: Background