presto-parquet/src/main/java/io/prestosql/parquet/ParquetEncoding.java/ParquetEncoding/getValuesReader
class ParquetEncoding:        @Override
        public ValuesReader getValuesReader(ColumnDescriptor descriptor, ValuesType valuesType)
        {
            checkArgument(descriptor.getPrimitiveType().getPrimitiveTypeName() == BINARY, "Encoding DELTA_LENGTH_BYTE_ARRAY is only supported for type BINARY");
            return new DeltaLengthByteArrayValuesReader();
        }