MongoDB sort() in golang

Introduction

This program demonstrates usage of sort method of MongoDB in golang

create application directory for golang application, and create init go module as below

mkdir mongodbsort
cd mongodbsort
go mod init github.com/freedomtutorials/mongodbsort

import mongodb-drivers in go module, for this issue the below command

go get go.mongodb.org/mongo-driver

We will be using the below Person structure in this article.

type Person struct 
{
	ID int
	FirstName string
	LastName string
	Age int
	Salary int
}

for this example, the below is the data we are using, prepare slice and insert into MongoDB collection

    var persons []Person  
	
    persons = append( persons, Person{ ID:1, FirstName:"Michael", LastName:"Ackerman", Age: 26, Salary: 1200})
    persons = append( persons, Person{ ID:1, FirstName:"Kayden", LastName:"Brown", Age: 24, Salary: 1200})
    persons = append( persons, Person{ ID:1, FirstName:"Dereck", LastName:"Belizaire", Age: 29, Salary: 1300})
    persons = append( persons, Person{ ID:1, FirstName:"Galilea", LastName:"Agrinsoni", Age: 23, Salary: 1400})
    persons = append( persons, Person{ ID:1, FirstName:"Jeremiah", LastName:"Albarracin", Age: 23, Salary: 1400})
    persons = append( persons, Person{ ID:1, FirstName:"Arianna", LastName:"Aliendo", Age: 28, Salary: 2300})
    persons = append( persons, Person{ ID:1, FirstName:"Aleida", LastName:"Anderson", Age: 30, Salary: 3000})
    persons = append( persons, Person{ ID:1, FirstName:"Calahn", LastName:"Anderson", Age: 33, Salary: 3300})
    persons = append( persons, Person{ ID:1, FirstName:"Hafeez", LastName:"Apata", Age: 35, Salary: 2500})
    persons = append( persons, Person{ ID:1, FirstName:"Leah", LastName:"Aristhilde", Age: 31, Salary: 2000})
	
    for _, person := range persons {
        //fmt.Printf( "%T  %T\n",  i, person)
        collInsertResult, err := coll.InsertOne( context.TODO(), person)
		
        if err != nil {
            log.Fatal(err)
        }
		
        fmt.Println("Inserted Single Document: ", collInsertResult.InsertedID)
    }

Sort collection on firstname

// set sort field and order, 1 = asc -1 = desc 
opts := options.Find()
opts.SetSort(bson.D{{"firstname", -1}})

// pass opts to Find Method
cursor, err := mydataCollection.Find( context.TODO(), bson.M{}, opts)

check for any error

if err != nil {
    log.Fatal(err) 
}

Read.All from cursor and fill Slice object

var persons []Person
if err = cursor.All( context.TODO(), &persons); err != nil {
    log.Fatal(err)
}

close the cursor

cursor.Close( context.TODO())