Earning Points. Starwood's Preferred Guest program is fairly straightforward: the more nights you spend at participating hotels, the faster you'll earn a free night.
As seen in the EXECUTING phase, the map will write (using Mapper.Context.write()) its output into a circular in-memory buffer (MapTask.MapOutputBuffer). The size of this buffer is fixed and determined by the configuration parameter mapreduce.task.io.sort.mb (default: 100MB).
Using the default input format. The Mapper class is a generic type with four formal type parameters that specify the input key, input value, output key, and output value types of the map function, as shown below. public class MaxTemperatureMapper extends Mapper<LongWritable, Text, Text, IntWritable>