在node js中使用mongo数据库进行分页

Question

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)
})
}

我想在这个功能上添加限制和页面，请帮助我

Answer 1

要添加分页，可以在aggregate方法中使用$skip和$limit。

$skip跳过特定数量的文档;$limit限制传递到管道下一阶段的文档数量。

他是你函数的更新版本:

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)
})
}

Answer 2

你可以这样做:

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 }],
},
},
])

注意$facet阶段的使用，它允许我们返回总记录计数，以及请求页面的所有文档。