Query Mongo collection for all documents with empty array nested in an array

Question

I have documents that look like this in a collection called movies:

{
  "_id" : ObjectId("51c272623021490007000001"),
  "movies": [
    {
      "name": "Booty Call"
      "play_times": []
    },
    {
      "name": "Bulletproof"
      "play_times": [{...},{...}]
    }
  ]
}

I would like to query for documents where "play_times" is not empty or null. Basically I only care about movies with play times.

sashkello · Accepted Answer · 2013-09-14 16:44:24Z

1

If you want to query for separate array elements within documents, that is not possible AFAIK. If you want to get documents which have non-empty play_times, then use $size operator:

movies.play_times : { $size : { $gt : 0} }

To check if field exists, there is an $exists operator.

answered Sep 14, 2013 at 16:44

sashkello

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3 Comments

Tony Over a year ago

Will this return documents who have one or more non-empty play_times or documents whose movies ALL have non-empty play_times?

sashkello Over a year ago

Try it and find yourself :) AFAIK, it will return those which have at least one non-empty movie. MongoDB is not very good at querying of nested arrays unfortunately... You may want to redesign your database to flatten it out (MongoDB is good at flat redundant records which don't need joins, because they already look like joined tables - try it).

Tony Over a year ago

It didn't work so I was wondering what you expected. Of course I'm going to try it myself

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