如何在猫鼬中执行“每个”查询

Question

Let's say I have a database with the a field of a document containing the following

new Test({fruits: [ 'apple', 'orange', 'banana']})

I want to query the fruits array by another array, making sure that the array passed into the query contains every item in the fruit database.

In plain JavaScript I would do the following:

var target = [ 'apple', 'orange', 'banana'];

var fruit2 = [ 'apple', 'orange', 'banana', 'peach']; // true
var fruit3 = [ 'mango', 'lemon', 'pineapple']; // false
var fruit4 = [ 'banana', 'apple', 'orange']; // true

const result = target.every(targetElem => fruit2.includes(targetElem));
console.log(result);

I can't use $in because it goes through each item in the query array making sure all items exist. In my case, I don't mind if the queried array contains extra items, as long as it has the same ones as the array in the database.

Answer 1

If you are using MongodB version 3.6+, you could use $expr with $map , $allElementsTrue , and $in to evaluate each member of the array in each document against your query array.

db.collection.find({
    $expr:{
        $allElementsTrue:{
            $map:{
                input: "$fruits",
                in: {$in: ["$$this", [ 'apple', 'orange', 'banana', 'peach']]}
            }
         }
    }
})

This will probably not be very efficient.

Playground

Edit :

An alternate way to do this that could use an index, at least in part:

db.collection.find({fruits:{$all:[ 'apple', 'orange', 'banana', 'peach']}})