How to implement Transactions in Sequelize/PostgreSQL and Node.Js?

Transactions in database, is a process to perform multiple or group of operations as a unit, which means you can execute multiple queries in one unit. Also we can rollback all the transactions if in case of any error or exceptions. In this article we will learn how to implement Transactions in our DB using Sequelize.
Sequelize provides a very easy way to implement transactions.

Let's get started.

What is Transactions:

Transactions is a process to perform multiple or group of operations as a unit, which means you can execute multiple queries in one unit. Also we can rollback all the transactions if in case of any error or exceptions.

First we need to establish the connection of postgreSQL with the DB using below codes:

File: /models/index.js

                        const Sequelize = require('sequelize'); 
                        const connection = {};
                        const sequelize = new Sequelize('MY_POSTGRES_DB_NAME', 'MY_POSTGRES_USERNAME', 'MY_POSTGRES_PASSWORD', {
                            host: 'localhost',
                            dialect: 'mysql',
                            operatorsAliases: 'false',
                            logging: false
                        });
                        
                        connection.sequelize = sequelize;
                        connection.Sequelize = Sequelize;
                        
                        module.exports = connection;
                        

Process or steps in Transactions:

There are 3 process or steps in Transactions.

1. Creating a transaction

2. Committing a transaction

3. Rollback a transaction

Let's have a look of the above steps.

1. Creating a transaction

In this process, we initialze the transaction. Here we will ensure that our transaction should start. To start the transactions we'll use the following statements.

                              const { sequelize } = require('../models');  
                              const transaction = await sequelize.transaction();
                            

2. Committing a transaction

In this we'll commit our transaction. Commiting transaction is responsile to make your changes and executing your statements. We'll use following statement to commit our transactions.

                          await transaction.commit();
                        

3. Rollback a transaction

If we get any error or any kind of exceptions occured, then we'll rollback our transaction, so that our transaction will be uncommited and nothing changes will be happen in our DB. It means no operation will be performed. We'll use following statement to rollback our transactions.

                              await transaction.rollback();
                            

Implement Transactions:

Now it's time to combined all the above steps of transactions to implement the transactions. In this, we will see How to implement Transactions in Sequelize/PostgreSQL and Node.Js.

Here we will write a function to implement transaction, in this function, we will register a user and when user is created we will add his address in DB. If both register and address creation will be done, then we will commit our transaction then both operation will be done. If we get any error or exceptions in our catch block we will rollback our transaction then nothing will be happend, no data will be inserted into our DB neither in Users table nor UserAddress table.

Let's see the codes:

                      const { sequelize } = require('../models') // import connection from /models/index.js
                      async function registerUser() {
                          let transaction;
                          try {
                              transaction = await sequelize.transaction();
                              const user = await Users.create({
                                  name: 'Shubham Verma'
                              }, { transaction });
                      
                              await UserAddress.create({
                                  address: 'Cyber City, Gurgaon, India',
                                  user_id: user.id
                              }, { transaction });
                      
                              await transaction.commit(); 
                      
                          } catch (error) {
                              if(transaction) {
                                 await transaction.rollback();
                              }
                          }
                      }
                    
                    

---

Conclusion:

In this article we learned what is transaction and How to implement Transactions in Sequelize/PostgreSQL and Node.Js?
We have implemented our transaction saw how transaction works.