MongoDB: How to get the last updated timestamp of the last updated document in a collection

Question

Is there a simple OR elegant method (or query that I can write) to retrieve the last updated timestamp (of the last updated document) in a collection. I can write a query like this to find the last inserted document

db.collection.find().limit(1).sort({$natural:-1})

but I need information about the last updated document (it could be an insert or an update).

I know that one way is to query the oplog collection for the last record from a collection. But it seems like an expensive operation given the fact that oplog could be of very large size (also not trustworthy as it is a capped collection). Is there a better way to do this?

Thanks!

Remember that the [natural order is not reliable](https://stackoverflow.com/a/33018164/174843), so it's best not to use it at all. — Vince Bowdren, May 02 '18 at 12:55

score 10 · Answer 1 · answered Dec 06 '17 at 09:38

10

You could get the last insert time same way you mentioned in the question:

db.collection.find().sort({'_id': -1}).limit(1)

But, There isn't any good way to see the last update/delete time. But, If you are using replica sets you could get that from the oplog.

Or, you could add new field in document as 'lastModified'. You can also checkout collection-hooks. I hope this will help

answered Dec 06 '17 at 09:38

Anirudh Bagri

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oplog is not always a trustable source (capped collection it is). Thanks anyway. – void Dec 06 '17 at 09:42
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You can get ObjectID timestamp with `ObjectId("507c7f79bcf86cd7994f6c0e").getTimestamp()` – clopez Oct 17 '19 at 12:36

score 5 · Answer 2 · answered Dec 30 '18 at 07:46

One way to go about it is to have a field that holds the time of last update. You can name it updatedAt. Every time you make an update to the document, you'll just update the value to the current time. If you use the ISO format to store the time, you'll be able to sort without issues (that's what I use).
The other way is the _id field.

Method 1 db.collection.find().limit(1).sort({updatedAt: -1})

Method 2 db.collection.find().limit(1).sort({_id: -1})

Damini Suthar · Answer 3 · 2017-12-06T09:08:04.207

-2

You can try with ,

db.collection.findOne().sort({$natural:-1}).limit(1);

edited Dec 06 '17 at 09:08

answered Dec 06 '17 at 08:19

Damini Suthar

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This will return only the 1st document in the collection. – Anirudh Bagri Dec 06 '17 at 08:25
You can check with the output @AnirudhBagri – Damini Suthar Dec 06 '17 at 08:42
@DaminiSuthar I don't have a field in every document containing the timestamp it got last updated. (I believe that is what you're assuming here) – void Dec 06 '17 at 08:45
Check edited , I have added timestamp field for that – Damini Suthar Dec 06 '17 at 08:47
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findOne.sort() is not valid. I believe you're talking about find().sort(). Please read my question again as I have mentioned the same query and why it doesn't work for me. – void Dec 06 '17 at 08:48
I have applied the same formula with using mongoose , try With , db.collection.find().sort({$natural:-1}).limit(1); – Damini Suthar Dec 06 '17 at 08:51
Remember that the [natural order is not reliable](https://stackoverflow.com/a/33018164/174843), so it's best not to use it at all. – Vince Bowdren May 02 '18 at 12:55

MongoDB: How to get the last updated timestamp of the last updated document in a collection

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