Multiple Counts with single query in mongodb

Question

I am new to Mongo Db and would appreciate some help with this query. I have been sifting through posts here for the past couple of days tearing my hair to see if I could find anything related to my query but with no luck.

I have a collection with documents similar in structure to below :

_id: xyz
Movieid: 123
MovieName: Titanic
ReleaseDate: 2000-01-01

_id: uvw
Movieid: 456
MovieName: Titanic II
ReleaseDate: 2018-01-01

_id: pqr
Movieid: 789
MovieName: Titanic III
ReleaseDate: 

I would like to achieve the output as counts for totalmovies, movies with release date, and movies without release date in 3 seperate columns as below:

Total   |   Released  |     UnReleased
 3      |       2     |          1

I was able to write individual queries to execute the counts, but I am unable to successfully consolidate all that into a single query. The end goal is to create one view producing these counts as output. I have tried using operators such as $and, but can't seem to get the query to work as desired....this is as far as I got :

db.getCollection("Movies").aggregate({
  "$and": [
    { "$match": { "ReleaseDate": { "$exists": true } }},
    { "$count": "Total" },
    { "$match": { "ReleaseDate": { "$exists": true, "$nin": [""] } }},
    { "$count": "Released" },
    { "$match": { "ReleaseDate": { "$exists": true, "$in": [""] } }},
    { "$count": "Unreleased" }
  ]
})

Answer 1

You can try below $facet aggregation

$count aggregation will always give you the counts for only single matching ($match) condition. So you need to further divide your each count into multiple section and that's what the $facet provides by processes multiple aggregation pipelines within a single stage on the same set of input documents.

db.collection.aggregate([
  { "$facet": {
    "Total": [
      { "$match" : { "ReleaseDate": { "$exists": true }}},
      { "$count": "Total" },
    ],
    "Released": [
      { "$match" : {"ReleaseDate": { "$exists": true, "$nin": [""] }}},
      { "$count": "Released" }
    ],
    "Unreleased": [
      { "$match" : {"ReleaseDate": { "$exists": true, "$in": [""] }}},
      { "$count": "Unreleased" }
    ]
  }},
  { "$project": {
    "Total": { "$arrayElemAt": ["$Total.Total", 0] },
    "Released": { "$arrayElemAt": ["$Released.Released", 0] },
    "Unreleased": { "$arrayElemAt": ["$Unreleased.Unreleased", 0] }
  }}
])

Output

[{
    "Total": 3,
    "Released": 2,
    "Unreleased": 1
}]