Sending the following to a DataTable shows the Group function has no effect, all records are returned rather than how a direct MySQL groups stuff:

	   $this->src("config")->query(DB::table('history'))
		   ->pipe($this->dataStore("tbl"))
		   ->pipe(new Group(array(
				"by"=>"name",
			        "sum" =>"amount"
			)));
		   

It gives same result as when I remove the last pipe. How can this be fixed?