MongoDB - Unwind array using aggregation and remove duplicates

Question

I am unwinding an array using MongoDB aggregation framework and the array has duplicates and I need to ignore those duplicates while doing a grouping further.

How can I achieve that?

question from:https://stackoverflow.com/questions/18804404/mongodb-unwind-array-using-aggregation-and-remove-duplicates

Answer 1

you can use $addToSet to do this:

db.users.aggregate([
  { $unwind: '$data' },
  { $group: { _id: '$_id', data: { $addToSet: '$data' } } }
]);

It's hard to give you more specific answer without seeing your actual query.