Use the following syntax:
--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 engine, Sqoop ignores the argument. Sqoop creates map tasks based on the number of intermediate files that the Blaze engine creates.