title: in which case one would use uncompress codec for parquet files in spark
body: <p>I'm new in Spark and trying to understand how different compression codecs work. I'm using Cloudera Quickstart VM 5.12x, Spark 1.6.0 and Python APIs.</p>
  
  <p>If I compress and save as Parquet files using below logic:</p>
  
  <pre><code>sqlContext.setConf("spark.sql.parquet.compression.codec","snappy")
  df.write.parquet("/user/cloudera/data/orders_parquet_snappy")
  </code></pre>
  
  <p>then I can read them as:</p>
  
  <pre><code>sqlContext.read.parquet("/user/cloudera/data/orders_parquet_snappy").show()
  </code></pre>
  
  <p>I believe above read doesn't need to uncompress and read. I wonder why and in which condition I will use uncompressed ?</p>
  
  <pre><code>sqlContext.setConf("spark.sql.parquet.compression.codec", "uncompressed")
  </code></pre>
  
  <p>Not sure if my understanding is correct. </p>