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How to find duplicate records in MongoDB?

To find duplicate entries in MongoDB based on the code and user_id fields, you can use the aggregate method along with the $group and $match pipeline stages. Here is an example of how to do this:

Let's take the example collection - user_collection.


    {
            "_id" : ObjectId("640054ef881f521a7b68fc96"),
            "code" : "google_uploader",
            "user_id" : "33052",
            "type" : "uploader",
            "charge_type" : "Prepaid",
            "available_credits" : 500,
            "total_used_credits" : 0
    }
    {
            "_id" : ObjectId("640054ef881f521a7b68fc99"),
            "code" : "google_uploader",
            "user_id" : "33052",
            "type" : "uploader",
            "charge_type" : "Prepaid",
            "available_credits" : 500,
            "total_used_credits" : 0
    }
    {
            "_id" : ObjectId("640054ef881f521a7b68fc95"),
            "code" : "shopify_importer",
            "user_id" : "33052",
            "type" : "importer",
            "charge_type" : "Prepaid",
            "available_credits" : 1,
            "total_used_credits" : 0
    }


The following MongoDB aggregation pipeline can be used to achieve this:

   
    db.user_collection.aggregate([
        {
            $group: {
                _id: { code: "$code", user_id: "$user_id" },
                count: { $sum: 1 },
                ids: { $push: "$_id" }
            }
        },
        {
            $match: {
                count: { $gt: 1 },
                "_id.user_id": "33052"
            }
        }
    ])
   

This will return all documents that have the same code and user_id fields and where the user_id is equal to "33052". The result will include an array of _id values for each duplicate entry found. Replace user_collection with the name of the collection where the documents are stored.

Based on the given query and the sample data in the user_collection collection, the output of the query will be:


    {
        "_id": {
        "code": "google_uploader",
        "user_id": "33052"
        },
        "count": 2,
        "ids": [
        ObjectId("640054ef881f521a7b68fc96"),
        ObjectId("640054ef881f521a7b68fc99")
        ]
    }
 

This output indicates that there are two duplicate records in the collection with the same code and user_id values. The ids array provides the _id values for each of the duplicate records.

How to find duplicate entries in MongoDB if the user_id value is unknown?

To identify duplicate entries in MongoDB based on the code and user_id fields, even if the user_id value is unknown, use the aggregate method along with the $group and $match pipeline stages. Here's an example:


    db.user_collection.aggregate([
        {
        $group: {
            _id: { code: "$code", user_id: "$user_id" },
            count: { $sum: 1 },
            ids: { $push: "$_id" }
        }
        },
        {
        $match: {
            count: { $gt: 1 }
        }
        }
    ])


This will return all documents that have the same code and user_id fields, regardless of the user_id value. The result will include an array of _id values for each duplicate entry found. Replace user_collection with the name of the collection where the documents are stored.

How to Count Duplicate Entries in MongoDB?

To find the count of duplicate entries based on code and user_id, you can modify the above query to use the count() method:


    db.user_collection.aggregate([
        {
          $group: {
            _id: { code: "$code", user_id: "$user_id" },
            count: { $sum: 1 }
          }
        },
        {
          $match: {
            count: { $gt: 1 }
          }
        },
        {
          $group: {
            _id: null,
            total_count: { $sum: 1 }
          }
        }
      ])
     

How to find duplicate records in MongoDB?

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