NODE - MONGO: getting last N entry, but older to newer

Question

i would like to get the last N entry from a collection, but ordered oldest to newer. If i just do:

.limit(N).sort({_id:-1})

it give me the the last N entry, but ordered from newest to oldest. I'm not using moongoose, but the mongo driver. Thank you.

Possible duplicate of [mongodb: how to get the last N records?](https://stackoverflow.com/questions/4421207/mongodb-how-to-get-the-last-n-records) — zero298, Aug 30 '18 at 15:43
I think that you should use `.sort()` before `.limit()` or it will `limit` the entries and then `sort` them — Orelsanpls, Aug 30 '18 at 15:45
@zero298 not really: i started from that but indeed the order you get is reverse compared to what i want. — piLeoni, Aug 30 '18 at 15:56

score 0 · Accepted Answer · answered Aug 30 '18 at 16:11

0

You can use aggregation - sort in descending order, limit, then sort in ascending order:

db.collection.aggregate([
    { $sort: { _id: -1 } },
    { $limit: N },
    { $sort: { _id: 1 } }
])

answered Aug 30 '18 at 16:11

Alex Blex

34,704
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score 0 · Answer 2 · answered Aug 30 '18 at 16:18

0

you can try this :

db.collection.find().skip(db.collection.count() - N)

answered Aug 30 '18 at 16:18

Arbaz Siddiqui

441
2
10

score 0 · Answer 3 · answered Aug 30 '18 at 17:33

0

This will order the results DESC by the _id field.

.limit(N).sort('-_id')

answered Aug 30 '18 at 17:33

moreirapontocom

458
3
10

score -1 · Answer 4 · answered Aug 30 '18 at 18:39

Initially i had:

db.collection(process.env.MESSAGES_COLLECTION).find(req.queryValues).sort({_id:-1}).limit(req.limit)

I've tried:

db.collection(process.env.MESSAGES_COLLECTION).find(req.queryValues).aggregate([
                {$sort: {_id: -1}},
                { $limit: req.limit},
                {$sort: {_id: 1}}])

But i got an error: TypeError: db.collection(...).find(...).aggregate is not a function

If i try:

db.collection(process.env.MESSAGES_COLLECTION).aggregate([
            {$find: req.queryValues},
            {$sort: {_id: -1}},
            { $limit: req.limit},
            {$sort: {_id: 1}}])

I get an empty array.

had to use $match inside aggregate instead of find() outside — piLeoni, Aug 31 '18 at 11:03

NODE - MONGO: getting last N entry, but older to newer

4 Answers4