presto-parquet/src/main/java/io/prestosql/parquet/reader/ParquetReader.java/ParquetReader/initializeColumnReaders
class ParquetReader:    private void initializeColumnReaders()
    {
        for (PrimitiveColumnIO columnIO : columns) {
            RichColumnDescriptor column = new RichColumnDescriptor(columnIO.getColumnDescriptor(), columnIO.getType().asPrimitiveType());
            columnReaders[columnIO.getId()] = PrimitiveColumnReader.createReader(column);
        }
    }