presto-rcfile/src/main/java/io/prestosql/rcfile/text/StructEncoding.java/StructEncoding/decodeElementValueInto
class StructEncoding:    private void decodeElementValueInto(int depth, int fieldIndex, BlockBuilder builder, Slice slice, int offset, int length)
            throws RcFileCorruptionException
    {
        // ignore extra fields
        if (fieldIndex > structFields.size()) {
            return;
        }

        if (isNullSequence(slice, offset, length)) {
            builder.appendNull();
        }
        else {
            structFields.get(fieldIndex).decodeValueInto(depth + 1, builder, slice, offset, length);
        }
    }