presto-record-decoder/src/main/java/io/prestosql/decoder/raw/RawRowDecoder.java/RawRowDecoder/decodeRow
class RawRowDecoder:    @Override
    public Optional<Map<DecoderColumnHandle, FieldValueProvider>> decodeRow(byte[] data, Map<String, String> dataMap)
    {
        return Optional.of(columnDecoders.entrySet().stream()
                .collect(toImmutableMap(
                        Map.Entry::getKey,
                        entry -> entry.getValue().decodeField(data))));
    }