title: How to publish single parquet file after processing in spark
body: <p>I have a parquet file having 100,000 records.
  I want to process all records with parallelism and my processing will generate some more columns.
  So if My parquet file has 3 columns and 100,000 records, my file looks like as below- </p>
  
  <pre><code>col A    col B     colC
  aa         bb       cc
  aa1        bb1      cc1
  </code></pre>
  
  <p>After getting processed in parallely , I want a new parquet file with same columns and 3more columns. My output looks like this -</p>
  
  <pre><code>col A    col B     colC     colD      colE       colF
  aa         bb       cc       dd        ee          ff
  aa1        bb1      cc1      dd1       ee1         ff1
  </code></pre>
  
  <p>I want to know -</p>
  
  <ul>
  <li>After running parallely in spark nodes, how can i combine all the results into 1 parquet file?</li>
  <li>How can i add more columns to an existing file?</li>
  </ul>
  
  <p>Any help would be appreciated.</p>