Extracting a value from an array of JSON objects in MongoDB [duplicate]

Question

Consider this:

{
  "movies": [
    {
      "title": "Star Wars",
      "year": 1977,
      "director": "George Lucas"
    },
    {
      "title": "The Empire Strikes Back",
      "year": 1980,
      "director": "Irvin Kershner"
    },
    {
      "title": "Return of the Jedi",
      "year": 1983,
      "director": "Richard Marquand"
    },
    {
      "title": "The Phantom Menace",
      "year": 1999,
      "director": "George Lucas"
    },
    {
      "title": "Attack of the Clones",
      "year": 2002,
      "director": "George Lucas"
    },
    {
      "title": "Revenge of the Sith",
      "year": 2005,
      "director": "George Lucas"
    },
    {
      "title": "The Force Awakens",
      "year": 2015,
      "director": "J.J. Abrams"
    }
  ]
}

I am trying to pull out all the movies directed by Geroge Lucas. This is what I have tried and it returns all items:

db.movies.find( {"movies.director" : "George Lucas"} ).pretty()

and also this which results in an error:

db.movies.find({"$pull" : {"movies.director" : "George Lucas"}}).pretty()

Please let me know how to query the database to retrieve only movies where the director key has "George Lucas" as the value.

Use $filter

s7vr
– s7vr

2017-01-29 21:49:29 +00:00
Commented Jan 29, 2017 at 21:49 — s7vr
– s7vr, Commented Jan 29, 2017 at 21:49
How can you do this?

JohnSnow
– JohnSnow

2017-01-29 22:13:17 +00:00
Commented Jan 29, 2017 at 22:13 — JohnSnow
– JohnSnow, Commented Jan 29, 2017 at 22:13
You need to use the $unwind aggregate function

Akinjide
– Akinjide

2017-01-29 22:33:53 +00:00
Commented Jan 29, 2017 at 22:33 — Akinjide
– Akinjide, Commented Jan 29, 2017 at 22:33

ares · Accepted Answer · 2017-01-29 22:26:13Z

3

You need to use aggregation framework:

db.movies.aggregate([
{
    $unwind : "$movies"
},
{
    $match : {
        "movies.director" : "George Lucas"
    }
},
{
    $project : {
        _id : 0,
        movies : 1
    }
}
])

edited Jan 29, 2017 at 22:26

answered Jan 29, 2017 at 22:20

ares

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3 Comments

JohnSnow Over a year ago

Throws an error when I run that.

ares Over a year ago

@JohnNoob: I missed the $ in unwind stage. Edited the answer. Should be fine now.

JohnSnow Over a year ago

Yep works now.. Just have to go read up on what the hell you did now

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