db-migration.js

require('dotenv').config();
const mongodbUri = require('mongodb-uri');
const {MongoClient} = require('mongodb');

async function runMigration(){
    const uri = process.env.DATABASE_URL;
    const uriObject = mongodbUri.parse(uri);
    const client = new MongoClient(uri,{ useNewUrlParser: true, useUnifiedTopology: true });
    try {
        await client.connect();
        const updatedSchema = await updateAccountSchema(client, uriObject.database);
        if(updatedSchema){
            console.log('The migration was successfully executed');
        }
    } catch (error) {
        console.error(error);
    } finally {
        await client.close();
    }
}

async function updateAccountSchema(client, database) {
    const accounts = await client.db(database).collection('accounts');

    const session = client.startSession();
    const transactionOptions = {
        readPreference: 'primary',
        readConcern: { level: 'local' },
        writeConcern: { w: 'majority' }
    };

    return new Promise(( async (resolve, reject) => {
        await session.withTransaction( async () => {
            const updatedAccounts = await accounts.updateMany(
                {
                    balance: { $type: ["double", "int", "decimal"] },
                    ngntBalance : { $exists: true }
                },
                [
                    {$set: {
                            balance: {
                                ETH: "$balance",
                                NGNT: "$ngntBalance"
                            }
                        }},
                    {$unset: ['ngntBalance']}
                ]
            );
            if(updatedAccounts.result.ok){
                resolve(updatedAccounts.result.ok)
            }else{
                reject(result.ok);
            }
        }, transactionOptions);
    }))
}

runMigration().catch(console.error);