Find duplicate records in MongoDB

Question

How would I find duplicate fields in a mongo collection.

I\'d like to check if any of the \"name\" fields are duplicates.

{
    \"name\" : \"ksqn291\         


        

Answer 1

You can find the list of duplicate names using the following aggregate pipeline:

• Group all the records having similar name.
• Match those groups having records greater than 1.
• Then group again to project all the duplicate names as an array.

The Code:

db.collection.aggregate([
{$group:{"_id":"$name","name":{$first:"$name"},"count":{$sum:1}}},
{$match:{"count":{$gt:1}}},
{$project:{"name":1,"_id":0}},
{$group:{"_id":null,"duplicateNames":{$push:"$name"}}},
{$project:{"_id":0,"duplicateNames":1}}
])

o/p:

{ "duplicateNames" : [ "ksqn291", "ksqn29123213Test" ] }