/**
* Clear tweets in elasticsearch
*
* @return bool
*/
public function clear()
{
$params = ['index' => $this->_esindex, 'type' => $this->_estype, 'body' => ['query' => ['match_all' => []]]];
$query = $this->_es->deleteByQuery($params);
// return $query['_indices']['tweets']['_shards']['successful'];
$result = true;
return $result;
}