Every entry in the params array has to exactly on array
of the bulk operation. An example param array would be:
array(
array('index' => array('_index' => 'test', '_type' => 'user', '_id' => '1')),
array('user' => array('name' => 'hans')),
array('delete' => array('_index' => 'test', '_type' => 'user', '_id' => '2'))
);
private function flushBulk()
{
$this->client->bulk($this->currentBulk);
$this->currentBulkSize = 0;
$this->currentBulk = [];
}