Question

The ______ file is populated with the key and a longwritable that contains the starting byte position of the record.

Answer 1

Your answer is index file, one of the most useful files.

Answer 2

Index.

An Index does not contain all the needed keys but just a set of keys.

You can define the indexInterval calling setIndexInterval() method.

The Index can be read entirely into the memory.

If you have a large map then you can set a index skip value also that can help to keep in memory just a small fraction of the index keys.

SetFile and ArrayFile are made on MapFile.

They can be implemented with just a few lines of code.

The SetFile rather than append(key, value) as only the key field append(key) and the value can always be the NullWritable instance.

The ArrayFile as only the value field append(value) and the key is a LongWritable that has the record number which is count + 1.