function _update(query, op, criteria, doc, options) {
  query.op = op;

  if (Query.canMerge(criteria)) {
    query.merge(criteria);
  }

  if (doc) {
    query._mergeUpdate(doc);
  }

  if (utils.isObject(options)) {
    // { overwrite: true }
    query.setOptions(options);
  }

  return query;
}
Executes a `replaceOne` Query
@returns the results