Restricts a query to a given range in the result set.
$start: The first entity from the result set to return. If NULL, removes any range directives that are set.
$length: The number of entities to return from the result set.
EntityFieldQuery The called object.
public function range($start = NULL, $length = NULL) {
$this->range = array(
'start' => $start,
'length' => $length,
);
return $this;
}