I have a document stored in MongoDB:
{
"id": 1,
"op": "someone",
"title": "some title",
"category": 1,
"conversation": {
"1": {
"user": 2,
"comment": "some comment"
},
"2": {
"user": 9,
"comment": "comment 2"
},
......
"26": {
"user": 5,
"comment": "comment 26"
}
}
}
I want to get this on request: (e.g. POST {"id":1, "page":2})
{
"id": 1,
"op": "someone",
"title": "some title",
"category": 1,
"conversation": {
"11": {
"user": 10,
"comment": "comment 11"
},
......
"20": {
"user": 25,
"comment": "comment 25"
}
}
}
i.e. 10 comments starting on 11, that is
page 1: return comments 1 - 10,
page 2: return comments 11 - 20,
......
page 10: return comments 91 - 100
I am using NodeJS. Since processing this in node can use up a lot of memory. I would like to do this in Mongo.
You can use the Mongo aggregation pipeline to do some powerful reshaping of documents.
It looks like the $redact stage would do what you want - there's a very similar example on the MongoDB site where they want to retrieve specific elements from arrays within documents.
In order to make that process on MongoDB side, you can use skip() and limit() function
const document_by_page = 10;
const page = 1;
db.collection.find().skip(page * document_by_page).limit(document_by_page);
With the new information from your comments, you should use mongo db pipeline to process information on MongoDB side. Take a look at https://docs.mongodb.com/manual/reference/operator/aggregation/filter/#mongodb-expression-exp.-filter.
Have a great day finding your solution