Pagination with aggregate search in mongoose - node.js

Question

const page = 1;
const limit = 10;
const searchResultsArray = await mongoose.connection.db
.collection('game_activity')
.aggregate([
{
$match: {
game_id
}
},
{
$addFields: {
activities: {
$filter: {
input: '$activity',
as: 'activity',
cond: {
$and: condition
}
}
}
}
},
{
$project: {
activities: 1,
activity_number: { <--- can't read property error
$size: '$activities'
}
}
},
{ $limit: 50 },
{
$facet: {
paginatedResult: [ { $sort: searchFilter }, { $skip: (page - 1) * limit } ]
}
}
])
.toArray();
const searchResultsObject = searchResultsArray[0];
if (
searchResultsObject.paginatedResult[0].activity_number === undefined ||
searchResultsObject.paginatedResult[0].activity_number == 0
) {
const result = {
no_activities: true
};
res.json(result);
} else {
const result = {
search_result: {
total_activities: searchResultsObject.paginatedResult[0].activity_number,
current_page: page,
last_page: Math.ceil(searchResultsObject.paginatedResult[0].activity_number / 10),
searched_activities: searchResultsObject.paginatedResult[0].activities
},
no_activities: false
};
res.json(result);
}
I have this .aggregate() search function and trying to apply the pagination result. This format worked on other search but on this aggregate() search, I have 2 problems.
console.log(searchResultsObject.paginatedResult[0]);
-------- result --------
{
search_result: {
total_activities: 16,
current_page: 1,
last_page: 2,
searched_activities: [
[Object], [Object],
[Object], [Object],
[Object], [Object],
[Object], [Object],
[Object], [Object],
[Object], [Object],
[Object], [Object],
[Object], [Object]
]
},
no_activities: false
}
const limit = 10 does not applied here. It returns all of the activities.
when I set the const page = 2;, I get TypeError: Cannot read property 'activity_number' of undefined this error and console.log(searchResultsObject.paginatedResult[0]); shows `undefined
I want to return 10 gaming activities per page, so in this case, if I set const page =2;, then it will return the rest 6 activities. I couldn't quite figure out how to fix this since this works on other .aggregate() search that I have.
------------ MongoDB Document ---------
{
"_id": {
"$oid": "601942d93aca6ee8cb300327"
},
"location_id": "ddff23323443",
"activity": [{
"activity_id": "VVINxmhRHsnMwvfT",
"created_by": {
"id": "aa332",
},
"activity_type": "league_of_legends",
"activity_info": {
"location_id": "ddff23323443",
"activity_time": "2021-02-02 05:45:00.000Z",
"game_code": "6"
},
"attendee": ["aa332"]
}, {
"activity_id": "EBZNKmsFKDgdeDz0",
"created_by": {
"id": "aa332",
},
"activity_type": "league_of_legends",
"activity_info": {
"id": "ddff23323443",
"activity_time": "2021-02-02 05:45:00.000Z",
"game_code": "6"
},
"attendee": ["aa332"]
}, {
"activity_id": "j8J1Jlk8MtWPi1HT",
"created_by": {
"id": "aa332",
},
"activity_type": "league_of_legends",
"activity_info": {
"location_id": "bvvsd33",
"activity_time": "2021-02-02 05:45:00.000Z",
"game_code": "6"
},
"attendee": ["aa332"]
}]
}
----- expectation -----
const page = 1
{
search_result: {
total_activities: 16,
current_page: 1,
last_page: 2,
searched_activities: [
[Object], [Object],
[Object], [Object],
[Object], [Object],
[Object], [Object],
[Object], [Object],
]
},
no_activities: false
}
const page = 2
{
search_result: {
total_activities: 16,
current_page: 2,
last_page: 2,
searched_activities: [
[Object], [Object],
[Object], [Object],
[Object], [Object],
]
},
no_activities: false
}

Answer 1

Your expectation is not clear as per your try, i can explain the basic pagination process,
pagination configs
const page = 1;
const limit = 10;
// If you are starting page number from 1 then you need to minus 1
const skip = (page - 1) * limit;
$unwind deconstruct activities array
$replaceRoot replace activities object to root
$sort documents
$facet to separate result, result data and count, $skip should before the $limit
const searchResultsArray = await mongoose.connection.db.collection('game_activity').aggregate([
{ $match: { _id: game_id } },
{
$project: {
activities: {
$filter: {
input: '$activity',
as: 'activity',
cond: { $and: condition }
}
}
}
},
{ $unwind: "$activities" },
{ $replaceRoot: { newRoot: "$activities" } },
{ $sort: searchFilter },
{
$facet: {
searched_activities: [
{ $skip: skip },
{ $limit: limit }
],
total_activities: [
{ $count: "count" }
]
}
}
]).toArray();
No data validation response
// No Data Fond!
if (!searchResultsArray[0].total.length) {
res.json({ no_activities: true });
return;
}
Success response
res.json({
search_result: {
total_activities: searchResultsArray[0].total_activities[0].count,
current_page: page,
last_page: Math.ceil(searchResultsArray[0].total_activities[0].count / limit),
searched_activities: searchResultsArray[0].searched_activities
},
no_activities: false
});
Combine above code together in sequence and try.