migrate.php

#!/usr/bin/env drush

$terms = array(
   27 => 318,
   28 => 319,
   29 => 320
);

foreach ($terms as $src => $dst) {
  $nids = taxonomy_select_nodes($src, FALSE, FALSE);
  $process = array();
  foreach ($nids as $nid) {
    $translations = translation_node_get_translations($nid);
    foreach ($translations as $translation) {
      $process[] = $translation->nid;
       print $translation->nid . "\n";
    }
  }
  $nodes = node_load_multiple($process);
  foreach ($nodes as $node) {
    $update = new stdClass();
    $update->nid = $node->nid;
    $update->type = $node->type;
    $update->field_erikoisruokavalio = $node->field_erikoisruokavalio;
    $update->field_ominaisuudet = $node->field_ominaisuudet;
    foreach ($node->field_ominaisuudet as $lang => $values) {
      foreach ($values as $idx =>$value) {
        $update->field_erikoisruokavalio[$lang][] = array(
         'tid' => $dst
        );
        unset($update->field_ominaisuudet[$lang][$idx]);
      }
    }
    field_attach_presave('node', $update);
    field_attach_update('node', $update);
  }
}