private function getChangesetValueFromDB(Tracker_FormElement_Field $field)
 {
     $dar = $this->getValueDao()->searchByFieldId($this->id, $field->getId());
     if ($dar && count($dar)) {
         $row = $dar->getRow();
         return $field->getChangesetValue($this, $row['id'], $row['has_changed']);
     }
     return null;
 }
 /**
  * @return \Tracker_Artifact_Changeset|null
  */
 public function getLastChangesetWithFieldValue(Tracker_Artifact $artifact, Tracker_FormElement_Field $field)
 {
     $dar = $this->dao->searchLastChangesetAndValueForArtifactField($artifact->getId(), $field->getId());
     if ($dar) {
         $row = $dar->getRow();
         $changeset = $this->getChangesetFromRow($artifact, $row);
         $value = $field->getChangesetValue($changeset, $row['value_id'], $row['has_changed']);
         $changeset->setFieldValue($field, $value);
         return $changeset;
     }
     return null;
 }