function checkForExistingData() {
  var movie = db.getSchema().table('Movie');
  var column = lf.fn.count(movie.id);
  return db.select(column).from(movie).exec().then(
      function(rows) {
        return rows[0][column.getName()] > 0;
      });
}
@return {!IThenable.<boolean>} Whether the DB is already populated with
sample data.