NullWritable is a special type of Writable representing a null value. No bytes are read or written when a data type is specified as NullWritable. So, in Mapreduce, a key or a value can be declared as a NullWritable when we don’t need to use that field.
What is NullWritable and how is it special from other Writable data types ?
NullWritable is a special type of Writable representing a null value. No bytes are read or written when a data type is specified as NullWritable. So, in Mapreduce, a key or a value can be declared as a NullWritable when we don’t need to use that field.
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Main driver class which provides job configuration parameters. Mapper class which must extend org.apache.hadoop.mapredu...
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This will be used to extract various date formats. The available date formats as follows. Syntax: to_char ( date , fo...