MongoDB collection find method doesn't work not in order-CodePudding

I am trying to get some db collection depends on users ID.

const chat = await Chat.findOne({ users });

now this will work : "users": ["630200a45d22133dbe5bec44", "630200975d22133dbe5bec41"]

but this will not work: "users": [630200975d22133dbe5bec41", "630200a45d22133dbe5bec44"]

Same id's, just not in the right order.

CodePudding user response：

You are looking for an exact match, so order matters. It seems what you want to be doing is to use $all, this checks all that the elements present in the input array exists in the db.

Additional you'll want to add a size check if you want to limit it so an exact match, otherwise documents like {"users": ["630200a45d22133dbe5bec44", "630200975d22133dbe5bec41", "otherid"] } will be matched.

Overall like so:

const chat = await Chat.findOne({
  users: {
    $all: [
      "630200975d22133dbe5bec41",
      "630200a45d22133dbe5bec44"
    ]
  },
  "users.2": {
    $exists: false
  }
})

Mongo Playground

Or dynamically based on input size:

const input = [
      "630200975d22133dbe5bec41",
      "630200a45d22133dbe5bec44"
    ];

const sizeKey = `users.${input.length}`

const chat = await Chat.findOne({
  users: {
    $all: input
  },
  [sizeKey]: {
    $exists: false
  }
})