presto-main/src/main/java/io/prestosql/operator/MultiChannelGroupByHash.java/MultiChannelGroupByHash/isRunLengthEncoded
class MultiChannelGroupByHash:    private boolean isRunLengthEncoded(Page page)
    {
        for (int i = 0; i < channels.length; i++) {
            if (!(page.getBlock(channels[i]) instanceof RunLengthEncodedBlock)) {
                return false;
            }
        }
        return true;
    }