Job optimization

Job optimization covers experience and skills to improve performance in the areas of job-running mode, JVM reuse, job parallel running, and query join optimizations.

Local mode

Hadoop can run in standalone, pseudo-distributed, and fully distributed mode. Most of the time, we need to configure it to run in fully distributed mode. When the data to process is small, it is an overhead to start distributed data processing since the launch time of the fully distributed mode takes more time than the job processing time. Since v0.7.0, Hive has supported automatic conversion of a job to run in local mode with the following settings:

> SET hive.exec.mode.local.auto=true; -- default false
> SET hive.exec.mode.local...