match exact item of array or only exact the combination of array items _ MongoDB

user_5677187 0
Viewed 50

suppose we have an array of some string. there is a use case It has to be done.

let myArray = ['a', 'g', 'd', 'e']

let collections = [

    {items:['a', 'b']},  ==> false

    {items:['a', 'g']}, ==> true

    {items:['d', 'f']},  ==> false

    {items:['a', 'g', 'd', 'e']}, ==> true

    {items:['a', 'g', 'd', 'e', 'o']}, ==> false

    {items:['a', 'g','e']}, ==> true

    {items:['g']}, ==> true

    {items:['g', 'k']}, ==> false
]

my goals:

  1. only exact match with one item.
  2. match the only combination of these items.

first of all, I know this query is so expensive cause for every item of this array we have factorial of that query match.

if we have 2 elements in our array we have 2 possible queries. if we have 4 elements we have 4 * 3 * 2 * 1 possible queries.

my second question is: is this relevant? beside of the use case.

mongoose mongodb
1 Answers

You can easily achieve this using $setIsSubset

db.collection.aggregate([
    {
        $addFields: {
            filteredCollections: {
                $filter: {
                    input: "$collections",
                    as: "collection",
                    cond: {
                       $setIsSubset: [
                          ["$$collection.items"],
                          ["a", "g", "d", "e"]
                       ]
                   }
                }
            }
        }
    },
    {
        $match: {
            "filteredCollections.0": {$exists: true}
        }
    }
])

For exact match you can use $all combined with $setIsSubset.

user_107703700
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