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mongodbcastingduplicatesmongodb-query
user3134277
user3134277

Reputation: 377

MongoDB : Find duplicate when field type is not the same

how can I detecte duplication even if the fields type are not the same ? 

{id : 1 , price : 5}
{id : 2 , price : "6"}
{id : 3 , price : "5"}

so duplicates are 

{id : 1 , price : 5}
{id : 3 , price : "5"}

Upvotes: 2

Views: 252

Answers (1)

Bertrand Martel
Bertrand Martel

Reputation: 45432

You can use $substr to do the conversion to String going from index 0 to -1 (rest of the string). : 

db.duplicates.aggregate(
    [{
        "$project": {
            id: 1,
            price: { $substr: ["$price", 0, -1] }
        }
    }, {
        "$group": {
            "_id": "$price",
            "count": { "$sum": 1 },
            "item": { $push: "$$ROOT" }
        }
    }, {
        "$match": {
            "_id": { "$ne": null },
            "count": { "$gt": 1 }
        }
    }]
)

The rest of the aggregation $group by $price to count the number of occurences and match items that have a count > 1 (duplicates). In item, you have the initial items that are duplicates :

{ "_id" : "5", "count" : 2, "item" : [ { "_id" : ObjectId("58616dc177b68a6c54252bc8"), "id" : 1, "price" : "5" }, { "_id" : ObjectId("58616dc177b68a6c54252bca"), "id" : 3, "price" : "5" } ] }

To count the number of distinct fields duplicated, add : 

{
    "$group": {
        "_id": null,
        "totalCount": {
            "$sum": 1
        }
    }
}

Upvotes: 1

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