CODEWITHSUNDEEP
mongodbmongodb-queryaggregation-framework
izmaylovdev
izmaylovdev

Reputation: 1880

Using document field as JS object field-name in aggregation pipeline

I have an JS object called tasksCountMap:

const tasksCountMap = {
   'Freshman': 46,
   'Senior': 10
}

and I need get count of task for each user type in my aggregation pipe, 'Freshman', 'Senior' it's document field called gradeLevel. I'm trying do it like this: 

status: {
        $let: {
          vars: {
            tasksCount: tasksCountMap['$gradeLevel'],
            completedTasksCount: '$completedTasksCount[0].count'
          },
          in: {
            $cond: {
              if: { $or: [
                { $eq: ['$$tasksCount', '$$completedTasksCount'] },
                { $lte: ['$$tasksCount', '$$completedTasksCount'] },
              ]},
              then: 'On track',
              else: 'High priority'
            }
          }
        }
      }

Also '$completedTasksCount[0].count' doesn't work to...

Can someone show right way to do this?

All pipeline: 

{
    $match: {
      type: 'student',
      counselorUserName: username
    },
    $project: {
      username: '$username',
      email: '$email',
      phone: '$phone',
      fullName: '$fullName',
      gradeLevel: {
        $switch: {
          branches: [{
              case: {
                $eq: ['$gradeLevel', '9']
              },
              then: 'Freshman'
            },
            {
              case: {
                $eq: ['$gradeLevel', '10']
              },
              then: 'Sophomore'
            },
            {
              case: {
                $eq: ['$gradeLevel', '11']
              },
              then: 'Junior'
            },
            {
              case: {
                $eq: ['$gradeLevel', '12']
              },
              then: 'Senior'
            }
          ],
          default: "Freshman"
        }
      }
    },
    $lookup: {
      from: 'RoadmapTasksCompleted',
      let: {
        username: '$username',
        gradeLevel: '$gradeLevel'
      },
      pipeline: [{
          $match: {
            monthToComplete: {
              $in: prevMonthsNames
            },
            $expr: {
              $and: [{
                  $eq: ['$username', '$$username']
                },
                {
                  $eq: ['$gradeLevel', '$$gradeLevel']
                }
              ]
            }
          }
        },
        {
          $count: 'count'
        }
      ],
      as: 'completedTasksCount'
    },
    $project: {
      username: '$username',
      email: '$email',
      phone: '$phone',
      fullName: '$fullName',
      completedTask: { $arrayElemAt: ['$completedTasksCount', 0] },
      status: {
        $let: {
          vars: {
            tasksCount: tasksCountMap['$gradeLevel'],
            completedTasksCount: '$completedTasksCount[0].count'
          },
          in: {
            $cond: {
              if: { $or: [
                { $eq: ['$$tasksCount', '$$completedTasksCount'] },
                { $lte: ['$$tasksCount', '$$completedTasksCount'] },
              ]},
              then: '$$tasksCount',
              else:'$$tasksCount'
            }
          }
        }
      }
    }
    $limit: 10,
    $skip: 10,
  }

Upvotes: 0

Views: 38

Answers (1)

s7vr
s7vr

Reputation: 75924

You have to move the js map into the aggregation pipeline for you to be able to access the map.

I split $project stage into two and took the liberty to clean up the status calculation.

Something like

{"$project":{
  "username":"$username",
  "email":"$email",
  "phone":"$phone",
  "fullName":"$fullName",
  "completedTask":{"$arrayElemAt":["$completedTasksCount",0]},
  "tasksCountMap":[{"k":"Freshman","v":46},{"k":"Senior","v":10}]
}},
{"$addFields":{
  "status":{
    "$let":{
      "vars":{
        "tasksCount":{
          "$arrayElemAt":[
            "$tasksCountMap.v",
            {"$indexOfArray":["$tasksCountMap.k","$gradeLevel"]}
           ]
         },
        "completedTasksCount":"$completedTask.count"
      },
      "in":{
        "$cond":{
          "if":{"$lte":["$$tasksCount","$$completedTasksCount"]},
          "then":"$$tasksCount",
          "else":"$$completedTasksCount"
        }
      }
    }
  }
}}

Upvotes: 1

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