SequenceFile is a flat file with binary key–value pairs that are widely used in MapReduce I/O formats. Internally, the map outputs are saved as SequenceFile. It has courses for Reader, Writer, and Sorter.
The following are the three SequenceFile formats:
- Key–value records that aren’t compressed.
- Only the ‘values’ are compressed in these compressed key–value records.
- Both keys and values are gathered in ‘blocks’ independently and compressed in block compressed key–value records. The size of the ‘block’ can be changed.