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I am trying to aggregate and reform the mongodb data and sort them based on the name. All the data belongs to same collection.

Node js, express js, mongodb

{ 
   "_id" : "1"
   "c_cat" : "one",
   "c_level" : "levelone",
   "c_group" : "groupone"
}

 { 
   "_id" : "2"
   "c_cat" : "one",
   "c_level" : "levelone",
   "c_group" : "grouptwo", 
 }

 { 
   "_id" : "3"
   "c_cat" : "one",
   "c_level" : "leveltwo",
   "c_group" : "groupthree", 
 }

 { 
   "_id" : "4"
   "c_cat" : "two",
   "c_level" : "leveltwo",
   "c_group" : "groupfour", 
 }

 { 
   "_id" : "5"
   "c_cat" : "two",
   "c_level" : "leveltwo",
   "c_group" : "groupfive", 
 }
  { 
   "_id" : "6"
   "c_cat" : "two",
   "c_level" : "levelfive",
   "c_group" : "groupfive", 
 }

The expected actual result after reshaping with nested structure should be as follows

{ 
   "c_cat" : "one"
    {
      "c_level" : "levelone"
        {
            "c_group" : ["groupone", "grouptwo"]
        }
      "c_level" : "leveltwo"
        {
            "c_group" : ["groupthree"]
        }
    }
}

{ 
   "c_cat" : "two"
    {
      "c_level" : "leveltwo"
        {
            "c_group" : ["groupfour", "groupfive"]
        }
      "c_level" : "levelfive"
        {
            "c_group" : ["groupfive"]
        }
    }
}

using the recommended script i get the excepted result

db.collection.aggregate([
  {
    "$group": {
      "_id": {
        "c_cat": "$c_cat",
        "c_level": "$c_level"
      },
      c_group: {
        $push: "$c_group"
      },
      "bookCount": {
        "$sum": 1
      }
    }
  },
  {
    "$group": {
      "_id": "$_id.c_cat",
      "c_level": {
        "$push": {
          "c_level": "$_id.c_level",
          "c_group": "$c_group"
        },

      },
      "count": {
        "$sum": "$bookCount"
      }
    }
  }
  ])

I used the same to pass and render the output to another page using below

router.get('/catalogue', function(req, res) {   

        var course = {};
        Ct_course.aggregate([


{
    "$group": {
      "_id": {
        "c_cat": "$c_cat",
        "c_level": "$c_level"
      },
      c_group: {
        $push: "$c_group"
      },
      "bookCount": {
        "$sum": 1
      }
    }
  },
  {
    "$group": {
      "_id": "$_id.c_cat",
      "c_level": {
        "$push": {
          "c_level": "$_id.c_level",
          "c_group": "$c_group"
        },

      },
      "count": {
        "$sum": "$bookCount"
      }
    }
  }
        ],
    function(err, results){  course = results;
    console.log(course); 
        res.render("course/catalogue",{course:course});
    });


});

The result i am getting in console is 

[ { _id: 'Safety',
    c_level: [ [Object], [Object], [Object], [Object] ],
    count: 13 },
  { _id: 'D Level',
    c_level: [ [Object], [Object], [Object], [Object], [Object] ],
    count: 18 },
  { _id: 'C Level',
    c_level: [ [Object], [Object], [Object], [Object] ],
    count: 45 },
  { _id: 'A Level', c_level: [ [Object] ], count: 1 },
  { _id: 'B Level', c_level: [ [Object], [Object] ], count: 18 },
  { _id: 'Special Courses',
    c_level:
     [ [Object],
       [Object],
       [Object],
       [Object],
       [Object],
       [Object],
       [Object],
       [Object],
       [Object] ],
    count: 34 } ]

The aggregate works fine in mongoshell, here it need to array array values to handlebar page

rakj
  • 59
  • 8
  • https://mongoplayground.net/p/aC0g3bAQ4Vc – Ashh May 22 '19 at 06:38
  • Hi thanks for the support. it works fine with mongodb environment but it is not working when i used in nodejs to pass the values – rakj May 22 '19 at 10:24
  • I am getting the _id value as null when tried to achieve the same using nodejs script – rakj May 22 '19 at 10:57
  • Please edit your question and show what you are trying to do with your code. – Ashh May 22 '19 at 11:00
  • I have updated the question.. two field c_level and c_group array values are not generated. using index value if arrays gives c_level value. – rakj May 24 '19 at 09:09

0 Answers0