I'm looking to make a perfect match between users using mongoose.

Here is an example of a schema:

username: "Nicolas",
fruitiwant:["apple", "orange"]
fruitihave: ["banana"]

I want to have a json that displays users who have a perfect match. User A wants the fruit that user B has. User B wants the fruit that user A has.

Thanks for your answers.

CodePudding user response：

What we can do is use $lookup to match all users from the collection that suffice the condition, we then just have to group to eliminate duplicate couples, like so:

db.collection.aggregate([
  {
    $lookup: {
      from: "collection",
      let: {
        ihave: "$bookihave",
        iwant: "$fruitiwant",
        id: "$_id"
      },
      pipeline: [
        {
          $match: {
            $expr: {
              $and: [
                {
                  $ne: [
                    "$_id",
                    "$$id"
                  ]
                },
                {
                  $gt: [
                    {
                      $size: {
                        "$setIntersection": [
                          "$$ihave",
                          "$fruitiwant"
                        ]
                      }
                    },
                    0
                  ]
                },
                {
                  $gt: [
                    {
                      $size: {
                        "$setIntersection": [
                          "$$iwant",
                          "$bookihave"
                        ]
                      }
                    },
                    0
                  ]
                }
              ]
            }
          }
        },
        {
          $project: {
            username: 1,
            
          }
        }
      ],
      as: "perfect"
    }
  },
  {
    $unwind: "$perfect"
  },
  {
    $project: {
      matchedUserNames: {
        $cond: [
          {
            $gt: [
              "$username",
              "$perfect.username"
            ]
          },
          [
            "$perfect.username",
            "$username",
            
          ],
          [
            "$username",
            "$perfect.username"
          ]
        ]
      }
    }
  },
  {
    $group: {
      _id: "$matchedUserNames"
    }
  }
])

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