updating field value of a content type with query
Why not you use field API field_attach_update() instead, it can save the node_save() process.

For example take this.

  $node = new stdClass();
  $node-&gt;id = $id_value;          // node id
  $node-&gt;type = $bundle_value;  // aka content type

  $node-&gt;field_fieldname[LANGUAGE_NONE][0]['value'] = 'some value';
  field_attach_update('node', $node);


Reference: http://www.urbaninsight.com/2011/10/24/saving-nodes-fields-without-saving-node-itself