@Override public UpdateRequest routing(String routing){
  if (routing != null && routing.length() == 0) {
    this.routing=null;
  }
 else {
    this.routing=routing;
  }
  return this;
}

@ Override public UpdateRequest routing ( String routing ) { if ( routing != null && routing . length ( ) == 0 ) { this . routing = null ; } else { this . routing = routing ; } return this ; }
controls the shard routing of the request . using this value to hash the shard and not the id .
