code: func dbPutIndexerTip(dbTx database.Tx, idxKey []byte, hash *chainhash.Hash, height int32) error {
  	serialized := make([]byte, chainhash.HashSize+4)
  	copy(serialized, hash[:])
  	byteOrder.PutUint32(serialized[chainhash.HashSize:], uint32(height))
  
  	indexesBucket := dbTx.Metadata().Bucket(indexTipsBucketName)
  	return indexesBucket.Put(idxKey, serialized)
  }
docs: // -----------------------------------------------------------------------------
  // The index manager tracks the current tip of each index by using a parent
  // bucket that contains an entry for index.
  //
  // The serialized format for an index tip is:
  //
  //   [<block hash><block height>],...
  //
  //   Field           Type             Size
  //   block hash      chainhash.Hash   chainhash.HashSize
  //   block height    uint32           4 bytes
  // -----------------------------------------------------------------------------
  // dbPutIndexerTip uses an existing database transaction to update or add the
  // current tip for the given index to the provided values.