我想查询我的帖子集合中的所有项目以查找最新评论。目前每个帖子都有一个嵌入式评论集合,像这样
{ "_id" : ObjectId("4f84b8da6c33f31122000001"), "comments" :
[{
"uname" : "bargledoofus",
"msg" : "hello hello hello",
"_id" : ObjectId("4fe926fa811ec70100008888"),
"date" : ISODate("2012-06-26T03:05:30Z")
},
{
"uname" : "bargledoofus",
"msg" : "moar hello",
"_id" : ObjectId("4fe9272b2f1efb0100000078"),
"date" : ISODate("2012-06-26T03:06:19Z")
},
{
"uname" : "bargledoofus",
"msg" : "most hello ever",
"_id" : ObjectId("4fe92cfd7614c8010000002b"),
"date" : ISODate("2012-06-26T03:31:09Z")
},
{
"uname" : "bargledoofus",
"msg" : "i think i've got it",
"_id" : ObjectId("4fe92d04f4a35c010000000e"),
"date" : ISODate("2012-06-26T03:31:16Z")
}
]}
如何查询帖子集合以获取最新评论、比某个日期时间更新的评论或评论属性(如comment.uname)?
我可以以某种方式使用 map reduce 来实现这一点吗?