title: Bytes Processed on Query explanation
body: <p>I have a "costly" query. I would like to optimize it (make it cheaper).
  I  ran the query and looked at the explanation which I find pretty useful for optimizing run times. </p>
  
  <p>My problem is as follows: for each stage, I see "Rows", but I do not see "Bytes Processed". As BQ charges by "Bytes Processed", I would like to optimize according to the processed data volume rather than # of records scanned.</p>
  
  <p>My question is: Is there a way to get this kind of info? (Volumes of read data in Bytes for every execution stage that actually reads data)</p>