func (q *Query) LogReplay() *Query {
	q.m.Lock()
	q.op.flags |= flagLogReplay
	q.m.Unlock()
	return q
}
func (q *Query) LogReplay() *Query {
	q.m.Lock()
	q.op.flags |= flagLogReplay
	q.m.Unlock()
	return q
}
// LogReplay enables an option that optimizes queries that are typically
// made on the MongoDB oplog for replaying it. This is an internal
// implementation aspect and most likely uninteresting for other uses.
// It has seen at least one use case, though, so it's exposed via the API.