Mongo find duplicates for entries for two or more fields

Question

I have documents like this:

{
    \"_id\" : ObjectId(\"557eaf444ba222d545c3dffc\"),
    \"foreing\" : ObjectId(\"538726124ba2222c0c0248ae\"),
    \"value\" :         


        

Answer 1

We only have to group on the bases of 2 keys, and select the elements with count greater than 1, to find the duplicates.

Query :- Will be like

db.mycollection.aggregate(
    { $group: { 
        _id: { foreing: "$foreing", value: "$value" },
        count: { $sum:  1 },
        docs: { $push: "$_id" }
    }},
    { $match: {
        count: { $gt : 1 }
    }}
)

OUTPUT :- Will be like

{
    "result" : [
        {
            "_id" : {
                "foreing" : 1,
                "value" : 2
            },
            "count" : 2,
            "docs" : [
                ObjectId("34567887654345678987"),
                ObjectId("34567887654345678987")
            ]
        }
    ],
    "ok" : 1
}

Reference Link :- How to find mongo documents with a same field