Filter keys not in collection

Question

How do we find keys which do not exist in collection.
Given an input list of keys ['3321', '2121', '5647'] , i want to return those that do not exist in the collection :

{ "_id" : { "$oid" : "5e2993b61886a22f400ea319" }, "scrip" : "5647" }
{ "_id" : { "$oid" : "5e2993b61886a22f400ea31a" }, "scrip" : "3553" }

So the expected output is ['3321', '2121']

aggregation pipeline has some functions to work with arrays https://docs.mongodb.com/v3.4/reference/operator/aggregation-array/ Please check if there is any you can use to filter your array. — Alex Blex, Jan 23 '20 at 12:50
It's either an aggregation or an app. What's your scale? For both dataset and the input array please. — Alex Blex, Jan 23 '20 at 13:08
Does this answer your question? [Present in input array](https://stackoverflow.com/questions/57526020/present-in-input-array) — whoami - fakeFaceTrueSoul, Jan 23 '20 at 16:44

score 1 · Answer 1 · answered Jan 23 '20 at 13:27

This aggregation gets the desired output (works with MongoDB version 3.4 or later):

INPUT_ARRAY = ['3321', '2121', '5647']

db.test.aggregate( [
{
  $match: {
    scrip: {
        $in: INPUT_ARRAY
    }
  }
},
{ 
  $group: { 
      _id: null, 
      matches: { $push: "$scrip" } 
  } 
},
{ 
  $project: {
      scrips_not_exist: { $setDifference: [ INPUT_ARRAY, "$matches" ] },
      _id: 0
  } 
}
] )

The output:

{ "scrips_not_exist" : [ "3321", "2121" ] }

Filter keys not in collection

1 Answers1