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Javascript – I am unable to get Mongoose Aggregate method to work

I am building an api and I wanted to use the skip and limit methods in mongoose to handle pagination.
I would like to get the total document size along with the pagination data. Initially, I made two queries: one for the paginated data and the other for total document size. This is bad, right? I started searching if there is an inbuilt way to handle this on a single query. I came across aggregate method. Unfortunately, I have not been able to get it to work.

Here are my codes with two queries:

const page = req.query.page
 const {skip, searchlimit} = getPagination(params);
let transactionsData = []

const transactions = await TransactionModel.find({transactionOwnerId: user?._id}).sort({createdAt:-1})
  .skip(skip)
  .limit(searchlimit);

 totalDocumentSize = await TransactionModel.countDocuments({transactionOwnerId:   user?._id});

  transactionsData = transactions as transactionAttributes[];

console.log(transactionsData, totalDocumentSize)

Here, I tried the aggregate method:

 const me = await TransactionModel.aggregate([{
           $match: {transactionOwnerId: user?._id}
        }, 
         {
            $sort: {createdAt:-1}
         }
        
     ]);
console.log(me);

I believe that I am not applying the aggredate method properly. It is returning an empty array. How can I use it to apply the skip and limit methods and also get the total document size?

Tags:

2

Answers


  1. 0

    You should try with $facet.

    Try this.I think it will work.

    const me = await TransactionModel.aggregate([
      { $match: { transactionOwnerId: user?._id } },
      {
        $facet: {
          transactions: [
            { $sort: { createdAt: -1 } },
            { $skip: skip },
            { $limit: limit },
          ],
          totalDocumentSize: [
            { $count: 'count' }
          ]
        }
      }
    ]);

    And then fetch each records using…

    const transactions = me[0].transactions;
const totalDocumentSize = me[0].totalDocumentSize[0]?.count || 0;

    Note :- Make sure to run this query inside async() function.

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  2. 0

    try this!

        const page = parseInt(req.query.page) || 1;
    const limit = 10;

    const transactions = await TransactionModel.aggregate([
      {
        $match: {
          $expr: { $eq: ["$transactionOwnerId", { $toObjectId: user?._id }] },
        },
      },
      {
        $facet: {
          data: [
            {
              $skip: (page - 1) * limit,
            },
            {
              $limit: limit,
            },
            {
              $sort: { createdAt: -1 },
            },
          ],
          count: [
            {
              $count: "count",
            },
          ],
        },
      },
    ]);

    console.log(transactions);
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