How to use match inside map function in Mongodb-CodePudding

I'm a beginner to Mongodb, I want to execute the following query to find the total number of assignments for each employee with assignment progress "working".

db.employees.aggregate([
  {
    "$lookup": {
      "from": "assignment",
      "localField": "empno",
      "foreignField": "emp_no",
      "as": "assignments"
    }
  },
  {
    $project: {
      points: {
        $sum: {
          $map: {
            input: "$assignments",
            in: { $match:{$Sthis.progress:"Working"}}
          }
        }
      },
      empno: 1
    }
  }
])

When I execute this query I get the error "Invalid $project:: caused by:: Unrecognized expression '$match'". How can I solve this?

CodePudding user response：

add filter to input of map and set condition in filter

db.employees.aggregate([
  {
    "$lookup": {
      "from": "assignment",
      "localField": "empno",
      "foreignField": "emp_no",
      "as": "assignments"
    }
  },
  {
    $project: {
      points: {
        $sum: {
          $map: {
            input:{"$filter":
            { "input": "$assignments", "as": "z", "cond": {$eq:["$$z.progress","Working"]} } },
            as :"s",
            in: "$$s"
          }
        }
      },
      empno: 1
    }
  
    
  }
])