How to remove except latest 10 record using Mongodb or mongoose lib?

Question

I'm using this query:

db.date.remove({
    _id:{ $not:{ $eq: ObjectId("570ba4f66931b8f21a8bf25f") }},
    date:{ $lt: outdated }
})

But it is not working properly. I don't need to give ids.

How to remove (delete) except latest 10 record?

Answer 1

It can be done by iterating on the sorted list of collection and you can continue for 10 or specified N records and then delete after it as db.collectionName.remove({_id:ObjectId(<IteratorID>)})

Let us see in the details from inserting the records and then proof of concept for deleting it

Inserting 19 records in a collection st2 (just for checking the correctness of the script) in mongo shell:

> for(var i =1; i<20;i++) { db.st2.insert({"a":i}) }
> 

Some of the records look likes as:

> db.st2.find()
{ "_id" : ObjectId("5c62e71d6ddb127f4e87dfc4"), "a" : 1 }
{ "_id" : ObjectId("5c62e7476ddb127f4e87dfc5"), "a" : 2 }
...
...

Just to iterate and print the values which will be deleted [This is only for script verification purposes]

> var counter = 0;
> var allRecords = db.st2.find().sort({ "_id" : -1});
> var totalElements= allRecords.count()
> for(var i = 0; i<totalElements; i++) { if (i<=10) {allRecords.next();continue;} var currentRecord = allRecords.next(); print(currentRecord._id); print(currentRecord.a)};
ObjectId("5c62e7476ddb127f4e87dfcb")
8
ObjectId("5c62e7476ddb127f4e87dfca")
7
ObjectId("5c62e7476ddb127f4e87dfc9")
6
....
....

In the place of printing the records with id, just delete it as db.collectionName.remove({_id:currentRecord._id}) check it below:

> var allRecords = db.st2.find().sort({ "_id" : -1});
> 
> var totalElements= allRecords.count()
> totalElements
19
> for(var i = 0; i<totalElements; i++) { if (i<=10) {allRecords.next();continue;} var currentRecord = allRecords.next(); db.st2.remove({_id:currentRecord._id});};
WriteResult({ "nRemoved" : 1 })
> var totalElements= allRecords.count()
> totalElements
11
>

Its deleted the older records and only left 11 records. just check the if condition and you can exactly left with N records or whatever you want.

Hope this will help you to understand it in better way, since I tried to cover it with full details so that you or someone might get benefited with these examples.