Question 247406 in Mongodb Question posted in
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how to find the value is not in mongodb, value is coming from constant array

I have an array like this

let arr = [a,b,c]

and a collection like this

{val:a},{val:b}

I want to know that document with val=c is not in the collection.

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2

Answers


  1. 0

    One option is:

    let arr = ['a', 'b', 'c'];
db.collection.aggregate([
  {$group: {_id: null, vals: {$addToSet: "$val"}}},
  {$project: {_id: 0, notIncluded: {$setDifference: [arr, "$vals"]}}}
])

    See how it works on the playground example

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  2. 0

    You could use filter, and a findOne for each value like:

    let arr = ["a","b","c"];
let notfound = arr.filter((value) => db.collection.findOne({val:value}) === null)

    Or you could use distinct with a filter:

    let arr = ["a","b","c"]
let existing = db.collection.distinct("val")
let notfound = arr.filter((value)=> existing.indexOf(value) == -1)
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