//appendHead add a infos generated from the record.
func appendHead(tx *bolt.Tx, rec *record.Head) {
	if find(rec) {
		return
	}
	k := rec.ToKey()
	err := db.Put(tx, "recent", k, rec)
	if err != nil {
		log.Print(err)
	}
}
//find finds records and returns index. returns -1 if not found.
func find(rec *record.Head) bool {
	k := rec.ToKey()
	var r int
	err := db.DB.View(func(tx *bolt.Tx) error {
		var err error
		r, err = db.Count(tx, "recent", k)
		return err
	})
	if err != nil {
		log.Print(err)
	}

	return r > 0
}