function getDigitalMigrationJoin(req, res, next) {
    DigitalMigrationForm.aggregate([
        // Join with user_info table
        {
            $lookup: {
                from: DigitalMigrationFormList.collection.name,       // other table name
                localField: "_id",   // name of users table field
                foreignField: "digitalFormId", // name of userinfo table field
                as: "forms"         // alias for userinfo table
            }
        },

    ]).exec(function (err, results) {
        console.log(results)
        res.send(results)

    })

}

i want to add pa gination on this function with limit and page please help me

CodePudding user response：

To add pagination, you cam use the $skip and $limit within the aggregate method.

$skip skips a specific number of documents; $limit limits the number of documents passed to the next stage in the pipeline.

He is an updated version of your function:

const getDigitalMigrationJoin = (req, res, next) => {
    // Extract page and pageSize parameters from the request query
    const page = req.query.page || 1;
    const pageSize = req.query.pageSize || 10;

    // Calculate skip and limit values based on the page and pageSize
    const skip = (page - 1) * pageSize;
    const limit = pageSize;

    DigitalMigrationForm.aggregate([
        // Join with user_info table
        {
            $lookup: {
                from: DigitalMigrationFormList.collection.name,       // other table name
                localField: "_id",   // name of users table field
                foreignField: "digitalFormId", // name of userinfo table field
                as: "forms"         // alias for userinfo table
            }
        },
        // Skip a specified number of documents
        { $skip: skip },
        // Limit the number of documents passed to the next stage
        { $limit: limit }
    ]).exec(function (err, results) {
        console.log(results)
        res.send(results)
    })
}

CodePudding user response：

You can do it like this:

const page = req.query.page || 1;
const pageSize = req.query.pageSize || 10;

DigitalMigrationForm.aggregate([
  {
    $lookup: {
      from: DigitalMigrationFormList.collection.name,      
      localField: "_id",  
      foreignField: "digitalFormId", 
      as: "forms",
    }
  },
  {
    $facet: {
      metadata: [{ $count: 'totalRecords' }],
      data: [{ $skip: (page - 1) * pageSize }, { $limit: pageSize }],
    },
  },
])

Note the use of $facet stage, that allows us to return both the total records count, as well as all the document for requested page.