我有一个关于当前工作项目的mongo问题需要你的帮助。下面是我的问题:我已将我的用户日志数据存储为示例:db.visitors集合[{uid:"0001",logPath:"/home",logTime:"MonDec27201018:51:22GMT+0000(UTC)"},{uid:"0002",logPath:"/",logTime:"MonDec27201018:51:22GMT+0000(UTC)"},{uid:"0001",logPath:"/product",logTime:"MonDec27201018:51:23GMT+0000(UTC)"},{uid:"0001",