title: How to find optimal number of mappers when running Sqoop import and export?
body: <p>I'm using Sqoop version 1.4.2 and Oracle database.</p>
  
  <p>When running Sqoop command. For example like this:</p>
  
  <pre><code>./sqoop import                               \
      --fs &lt;name node&gt;                         \
      --jt &lt;job tracker&gt;                       \
      --connect &lt;JDBC string&gt;                  \
      --username &lt;user&gt; --password &lt;password&gt;  \
      --table &lt;table&gt; --split-by &lt;cool column&gt; \
      --target-dir &lt;where&gt;                     \
      --verbose --m 2
  </code></pre>
  
  <p>We can specify <strong>--m</strong> - how many parallel tasks do we want Sqoop to run (also they might be accessing Database at same time).
  Same option is available for ./sqoop export &lt;...></p>
  
  <p><em><strong>Is there some heuristic (probably based on size of data) which will help to guess what is optimal number of task to use?</em></strong></p>
  
  <p>Thank you!</p>