A hardware-implemented file reader includes an interface, multiple hardware-implemented column readers and a hardware-implemented record reconstructor. The interface is configured to access a file including multiple records. The records store values in accordance with a nested structure that supports optional values and repeated values. The file is stored in a columnar format having multiple columns, each column storing (i) compressed values and (ii) corresponding compressed structure information that associates the values in the column to the nested structure of the records. Each column reader is configured to be assigned to a respective selected column, and to read and decompress both the values and the structure information from at least a portion of the selected column. The record reconstructor is configured to reconstruct one or more of the records from at least portions of the columns that are read by the column readers, and to output the reconstructed records.