Range based paging mongodb

Question

on the mongodb docs it says: (source)

Unfortunately skip can be (very) costly and requires the server to walk from the beginning of the collection,

Answer 1

The basic idea is to write the paging into the query predicate pattern.

For example if you list forum posts by date and you want to show the next page then use the date of the last post on the current page as a predicate. MongoDB can use the index built on the date field.

//older posts
db.forum_posts.find({date: {$lt: ..last_post_date..} }).sort({date: -1}).limit(20);

Of course this gets a little more complicated if the field you are using for sorting is not unique.