How Not To Update Existing Taxonomy Terms At Migration I am using migrate and migrate_d2d to migrate taxonomy terms from a d7 site to another d7 site.How can I specify in my migration that nothing be done if the term already exist in the target?
So far, in "prepare" function, I am querying the target to find out if the term already exist, but I am not sure if this is the right way to go about it or where to go from here.

function prepare($entity, stdClass $row) {
  $term_name = $entity-&gt;name; 
  $query_checking_if_term_exist = db_select('taxonomy_term_data', 'ttd')
    -&gt;condition('ttd.name', $term_name)
    /* TODO: fetch vid from taxonomy_vocabulary table instead of hardcoding it */
    -&gt;condition('ttd.vid', '2')
    -&gt;fields('ttd', array('name'));
  $term_exists = $query_checking_if_term_exist-&gt;execute()-&gt;fetchAll();
  if(isset($term_exists)) {
    //TODO
  }   
}
If found the solution, if the term exists return false from prepareRow($row) and the term won't be updated or migrated again. like this:

public function prepareRow($row) {
  if (parent::prepareRow($row) === FALSE) {
    return FALSE;
  }
  $term_name = $row-&gt;name;
  $query_checking_if_term_exist = db_select('taxonomy_term_data', 'ttd')
    -&gt;condition('ttd.name', $term_name)
    -&gt;condition('ttd.vid', '2')
    -&gt;fields('ttd', array('name'))
    -&gt;execute()-&gt;fetchAll();
  if(!empty($query_checking_if_term_exist)) {
    return FALSE;
  }


}