performing distinct on multiple fields in mongodb

Question

Let's say we have a collection of docs as follows :

[
{
"name" : "john",
"age" : 23,
"city": "New York",
"gender": "M"
},
{
"name" : "doe",
"age" : 30,
"city": "dubai",
"gender": "M"
},
{
"name" : "jean",
"age" : 23,
"city": "New York",
"gender": "F"
}
{
"name" : "phil",
"age" : 24,
"city": "Ohio",
"gender": "M"
}
]

Expected output :

{
"name" : ["john","doe","jean","phil"],
"age" : [23,30,24],
"city": ["New York","Dubai","Ohio"],
"gender": ["M","F"]
}

I tried using mongodb's distinct , but that will return me just uniques values for one particular field...I dont think we can pass multiple fields in distinct query...

Answer 1

The $addToSet is specifically for these kind of things.

db.coll.aggregate([
{$group: {
    _id: null,
    name: {$addToSet: '$name'},
    age: {$addToSet: '$age'},
    city: {$addToSet: '$city'},
    gender: {$addToSet: '$gender'}
    }}
])

which gives the output -

{ "_id" : null, "name" : [ "phil", "jean", "doe", "john" ], "age" : [ 24, 30, 23 ], "city" : [ "Ohio", "dubai", "New York" ], "gender" : [ "F", "M" ] }