Pagination with MongoDB in Node.js (With Sorting)

Question

Using suggestions from here and here, I'm trying to implement a scalable, paginating, stateless REST API in the following way:

//Page 1
db.users.find().limit(pageSize);
//Find the id of the last document in this page
last_id = ...

//Page 2
users = db.users.find({'_id'> last_id}).limit(pageSize);
//Update the last id with the id of the last document in this page
last_id = ...

It works in most cases, but the problem is I have to sort a list of videos according to view count and then try to paginate.

// Page 2
videos = db.videos.find({'viewCount'< last_view_count}).sort({viewCount : 'descending'}).limit(pageSize);

This does not work since there might be multiple items with same view count and some items will miss out when we do 'viewCount'< last_view_count

Any ideas on how to solve this problem would be appreciated :)

Possible duplicate of Calculate skip value for given record for sorted paging — Blakes Seven
– Blakes Seven, Commented Nov 24, 2015 at 4:36
Is there any way to achieve this in a state-less environment where each request can hit any of the servers in a cluster and run in isolation? — Harsha Bhat
– Harsha Bhat, Commented Nov 24, 2015 at 4:58
A session store or any kind of persistence is generally required for stateless requests. If you are not using cookie based sessions then you should be using a token in the request. The bottom line is the persisted store needs to be accessible to all worker nodes. That is a common practice in high-availability systems. — Blakes Seven
– Blakes Seven, Commented Nov 24, 2015 at 5:00

weiyin · Accepted Answer · 2015-11-24 06:11:38Z

4

You can sort and filter on a combination of fields that together uniquely identify documents. For example, sort on {viewcount: 'descending', _id: 'ascending'}, and filter on {viewcount <= last_view_count, _id > last_id}.

answered Nov 24, 2015 at 6:11

weiyin

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1 Comment

Harsha Bhat Over a year ago

Good answer. Just wondering, is there any way to extend this to a two-way backward/forward pagination? Ex. being able to get both page 2 and page 4 while having the page 3 response?

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