def _generate_schema(columns):
  """Generate a BigQuery schema with the configured columns."""
  m = {'stringValue': 'STRING', 'integerValue': 'INTEGER',
       'floatValue': 'FLOAT', 'booleanValue': 'BOOLEAN'}
  segments = []
  for col in columns:
    segments.append('{0}:{1}'.format(col['name'], m[col['type']]))
  return ', '.join(segments)