message: More logging to csv endpoint
diff: @@ -2061,6 +2061,7 @@ class Superset(BaseSupersetView):
  @log_this
  def csv(self, client_id):
  """Download the query results as csv."""
  + logging.info("Exporting CSV file [{}]".format(client_id))
  query = (
  db.session.query(Query)
  .filter_by(client_id=client_id)
  @@ -2074,14 +2075,20 @@ class Superset(BaseSupersetView):
  return redirect('/')
  blob = None
  if results_backend and query.results_key:
  + logging.info(
  + "Fetching CSV from results backend "
  + "[{}]".format(query.results_key))
  blob = results_backend.get(query.results_key)
  if blob:
  + logging.info("Decompressing")
  json_payload = utils.zlib_decompress_to_string(blob)
  obj = json.loads(json_payload)
  columns = [c['name'] for c in obj['columns']]
  df = pd.DataFrame.from_records(obj['data'], columns=columns)
  + logging.info("Using pandas to convert to CSV")
  csv = df.to_csv(index=False, encoding='utf-8')
  else:
  + logging.info("Running a query to turn into CSV")
  sql = query.select_sql or query.executed_sql
  df = query.database.get_df(sql, query.schema)
  # TODO(bkyryliuk): add compression=gzip for big files.
  @@ -2089,6 +2096,7 @@ class Superset(BaseSupersetView):
  response = Response(csv, mimetype='text/csv')
  response.headers['Content-Disposition'] = (
  'attachment; filename={}.csv'.format(query.name))
  + logging.info("Ready to return response")
  return response
  @has_access
  