MongoDB 在 Node.JS mongodb 驱动程序中按自定义计算排序

Question

I'm Using Node.JS MongoDB driver. I have a collection of job lists with salary and number of vacancies , I want to sort them according to one rule, if either salary or number of vacancies are greater they will get top priority in sorting, and I came up with this simple formula

( salary / 100 ) + num_of_vacancies

eg:

Top priority ones

{ salary: 5000 , num_of_vacancies: 500 }   // value is 550
{ salary: 50000 , num_of_vacancies: 2 }    // value is 502

And Less priority for

{ salary: 5000 , num_of_vacancies: 2 }     // value is 52

But my Problem is, As far as I know, MongoDB sort takes arguments only to sort in ascending or descending order and a property to sort. How do I sort with custom expression.

The data in MongoDB looks like this // not the full varsion

{
    title:"job title",
    description:"job description",
    salary:5000,
    num_of_vacancy:50
}

Answer 1

This is just an option. Adjust it for a mongo driver.

• $addFields we create the field to sort, named toSortLater just for semantic purposes.
• add a $sort stage, and sort high values first. Change to 1 for the opposite behaviour.

db.collection.aggregate([{
$addFields:{ 
toSortLater:{
   $add:[
       {$divide:["$salary", 100]}, 
       "$num_of_vacancies"]
}}}, {$sort:{"toSortLater":-1}}
])