How to remove duplicates based on a key in Mongodb

Question

I have a collection in MongoDB where there are around (~3 million records). My sample record would look like,

 { "_id" = ObjectId("50731xxxxxxxxxxxxxxxxxxxx"),
   "source_references" : [
                           "_id" : ObjectId("5045xxxxxxxxxxxxxx"),
                           "name" : "xxx",
                           "key" : 123
                          ]
 }

I am having a lot of duplicate records in the collection having same source_references.key. (By Duplicate I mean, source_references.key not the _id).

I want to remove duplicate records based on source_references.key, I'm thinking of writing some PHP code to traverse each record and remove the record if exists.

Is there a way to remove the duplicates in Mongo Internal command line?

Answer 1

Here is a slightly more 'manual' way of doing it:

Essentially, first, get a list of all the unique keys you are interested.

Then perform a search using each of those keys and delete if that search returns bigger than one.

    db.collection.distinct("key").forEach((num)=>{
      var i = 0;
      db.collection.find({key: num}).forEach((doc)=>{
        if (i)   db.collection.remove({key: num}, { justOne: true })
        i++
      })
    });