Querying the most recent posts in a MongoDB collection - mongodb

Question

Rather new to Mongodb/Mongoose/Node. Trying to make a query to retrieve the most recent posts (example being the 10 most recent posts) across all documents in a collection.
I tried querying this a few different ways.
MessageboardModel.find({"posts": {"time": {"$gte": ISODate("2014-07-02T00:00:00Z")}}} ...
I tried doing the above just to try getting to the proper nested time property, but everything I was trying throws an error. I'm definitely missing something here...
Here is an example document in the collection:
{
"_id": {
"$oid": "5c435d493dcf9281500cd177"
},
"movie": 433249,
"posts": [
{
"replies": [],
"_id": {
"$oid": "5c435d493dcf9281500cd142"
},
"username": "Username1",
"time": {
"$date": "2019-01-19T17:24:25.204Z"
},
"post": "This is a post title",
"content": "Content here."
},
{
"replies": [],
"_id": {
"$oid": "5c435d493dcf9281500cd123"
},
"username": "Username2",
"time": {
"$date": "2019-01-12T17:24:25.204Z"
},
"post": "This is another post made earlier",
"content": "Content here."
}
],
"__v": 0
}
There are many documents in the collection. I want to get, say the most recent 10 posts, across all of the documents in the entire collection.
Any help?

Answer 1

You can try using aggregation query:
Steps:
1> Match Specific doc
2> Stretch docs of its array using $unwind.
3> Sort using the time field from the posts.
4> Select fields , if specific fields needs to be shown.
5> Add limit, how many docs you want.
<YOUR_MODEL>.aggregate([
{$match:{
"movie": 433249 //you may add find conditions here, otherwise you can keep {} or remove $match from here
}},
{$unwind:"$posts"}, //this will make the each array element with different different docs.
{$sort:{"posts. time":1}}, // sort using the date field now, depends on your requirement use -1 /1
{$project:{posts:1}}, //select docs only from posts field. [u can remove if you want every element, or may modify]
{$limit:10} //you want only last 10 posts
]).exec();
let me know if you still having any issue or getting any error.
would love answer.