title: Spark output JSON vs Parquet file size discrepancy
body: <p>new Spark user here. i wasn't able to find any information about filesize comparison between JSON and parquet output of the same dataFrame via Spark.</p>
  
  <p>testing with a very small data set for now, doing a df.toJSON().collect() and then writing to disk creates a 15kb file. but doing a df.write.parquet creates 105 files at around 1.1kb each. why is the total file size so much larger with parquet in this case than with JSON?</p>
  
  <p>thanks in advance</p>