How to fetch count and resultsets using mongodb $match and $group

Question

How to get the resultsets on matching $match along with count . I am trying to get say initial 5 records with complete resultsets along with total number of matched records.

Here is my trial code:

let querySpec = [{
        $match: {
            entity: "project",
            roles: {
                $in: roles
            },
            deleteFlag: {
                $exists: false
            }
        }
    },
    {
        $group: {
            _id: null,
            count: { $sum: 1 }
        }
    },
    { $limit: event.rows },//5
    { $skip: event.first }//0

    ];

expected:

{[data:array[5],count:10]}

but getting :
{_id: null, count: 10}

tried using facets but it fails to fetch next result sets:

var querySpec = [
    {
        "$facet": {
            "data": [
                {
                    $match: {
                        entity: "project",
                        $or: [{
                            accessType: "Private",
                            userName: userName
                        }, {
                            accessType: "Public"
                        }],
                    }
                },

                { $limit: event.rows },
                { $skip: event.first },
                { $sort: { [event.sortField]: event.sortOrder } }
            ],
            "totalRecords": [
                {
                    $match: {
                        entity: "project",
                        $or: [{
                            accessType: "Private",
                            userName: userName
                        }, {
                            accessType: "Public"
                        }],
                    }
                },
                { "$count": "total" }
            ]
        }
    }

];

output: {data: Array(5), totalRecords: Array(1)} but for next pagination click it fails to fetch recordsets {data: Array(0), totalRecords: Array(1)}:

Answer 1

let querySpec = [
    {
        $match: {
            entity: "project",
            roles: {
                $in: roles
            },
            deleteFlag: {
                $exists: false
            }
        }
    }, {
        $facet: {
            'data': [ // the key in which you want your data
                // add sort here if needed
                {
                    '$skip': event.first
                }, {
                    '$limit': event.rows
                }
            ],
            'count': [
                {
                    '$count': 'count'
                }
            ]
        }
    }, {
        '$addFields': {
            'count': { // the key in which you want the count
                '$arrayElemAt': [
                    '$count.count', 0
                ]
            }
        }
    }]

try this it will remove the data which does not matched your query. Also skip should be used before limit.