MapFile in Pig

Question

What is the use of MapFile class in Pig?

Answer 1

MapFile is a class which serves file-based map from keys to values.

A map is a directory containing two files, the data file, containing all keys and values in the map, and a smaller index file, containing a fraction of the keys. The fraction is determined by MapFile.Writer.getIndexInterval().

The index file is read entirely into memory. Thus, key implementations should try to keep themselves small. Map files are created by adding entries in-order.