MongoDB count distinct value?

Question

Here below show my code. I have to calculate the how many times distinct value repeated. Here i have store distinct value in \"results\".I used collection.count() to calcula

Answer 1

To get occurrences of distinct values of a field 'field1' on a collection 'col1' and write to a separate collection 'distinctCount'. Also allow to use disk space in case the collection is huge.

db.col1.aggregate(
          [{$group: {
              _id: "$field1",
              count: { $sum : 1 }
            }}, {
            $group: {
              _id: "$_id",
              count: { $sum : "$count" }
            }},{
              $out: "distinctCount"
            }],
         {allowDiskUse:true}
)