How to filter a collection based on each array item in a doc field in Mongodb

Question

Let's say I have a collection, like so:

[
{ "_id": "101",  parts: [1.2, 2] },
{ "_id": "102",  parts: [2, 3.5] },
{ "_id": "103",  parts: [4.1, 10] }
]

What is the query I need to write so that each item in the array parts is greater than equal to the item with the same array index in an input array [1, 5]?

output would be:

[
{ "_id": "103",  parts: [4.1, 10] } // 4.1 >= 1 and 10 >= 5
]

is this possible? any idea?

The parts array and the input array have same number of elements? — prasad_
– prasad_, Commented Sep 16, 2020 at 8:53

mickl · Accepted Answer · 2020-09-16 09:02:37Z

1

You can use the dot notation and run following query for your example:

{"parts.0":{"$gte":1},"parts.1":{"$gte":5}}

Mongo Playground

or use below JS code to build something more generic:

let input = [1,5];
let query = Object.fromEntries(input.map((val, i) => ([ "parts." + i, { $gte: val } ])));

console.log(query);

answered Sep 16, 2020 at 9:02

mickl

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Cuong Le Ngoc · Accepted Answer · 2020-09-16 09:02:55Z

1

If you know the input array before query then you can create query object from it first then pass this object to the query:

let query = input.reduce((acc, cur, index) => {
  acc['parts.' + index] = { $gt: cur };
  return acc;
}, {});
// [1, 5] will create {"parts.0": {$gt: 1},"parts.1": {$gt: 5}}
db.collection.find(query)...

answered Sep 16, 2020 at 9:02

Cuong Le Ngoc

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