title: Reading parquet files from multiple directories in Pyspark
body: <p>I need to read parquet files from multiple paths that are not parent or child directories. </p>
  
  <p>for example, </p>
  
  <pre><code>dir1 ---
         |
         ------- dir1_1
         |
         ------- dir1_2
  dir2 ---
         |
         ------- dir2_1
         |
         ------- dir2_2
  </code></pre>
  
  <p><code>sqlContext.read.parquet(dir1)</code> reads parquet files from dir1_1 and dir1_2</p>
  
  <p>Right now I'm reading each dir and merging dataframes using "unionAll". 
  Is there a way to read parquet files from dir1_2 and dir2_1 without using <code>unionAll</code> or is there any fancy way using <code>unionAll</code></p>
  
  <p>Thanks</p>