Mongodb Aggregation count array/set size

Question

Here\'s my problem:

Model:

{ application: \"abc\", date: Time.now, status: \"1\" user_id: [ id1, id2, id4] }

{ application: \"abc\",

Answer 1

Sorry I'm a little late to the party. Simply grouping on the 'user_id' and counting the result with a trivial group works just fine and doesn't run into doc size limits.

[
    {$match: {application: 'abc', date: {$gte: startDate, $lte: endDate}}},
    {$unwind: '$user_id'},
    {$group: {_id: '$user_id'}},
    {$group: {_id: 'singleton', count: {$sum: 1}}}
];