The m or num-mappers argument defines the number of map tasks that Sqoop must use to import and export data in parallel.
Use the following syntax:
-m <number of map tasks>
--num-mappers <number of map tasks>
If you configure the m argument or num-mappers argument, you must also configure the split-by argument to specify the column based on which Sqoop must split the work units.
Use the m argument or num-mappers argument to increase the degree of parallelism. You might have to test different values for optimal performance.
When you configure the m argument or num-mappers argument and run Sqoop mappings on the Spark or Blaze engines, Sqoop dynamically creates partitions based on the file size.
If you configure the num-mappers argument to export data on the Blaze or Spark engine, Sqoop ignores the argument. Sqoop creates map tasks based on the number of intermediate files that the Blaze or Spark engine creates.