techedemic / type_orm_poc

Proof of Concept for TypeORM

TypeORM Proof-of-Concept (POC)

To run in development environment

• Ensure you have database. If not, create as follows (replace password/db name/etc as you see fit)

  • Log in to mysql

    mysql -u <admin_user_name> -p
    password:
    
    mysql>

  • Create a new database

    CREATE DATABASE typeorm_poc;

  • Create user to access typeorm_poc database only

    GRANT ALL ON typeorm_poc.* TO `poc_user`@`%` IDENTIFIED BY `poc_pass`

• The application uses the following environment variables. These will be taken from the environment (first). If not provided from cli environment, it will look for a .env file. The following values should be provided (sample values included):

  • TYPEORM_CONNECTION = mysql - Leave as mysql for purpose of this POC
  • TYPEORM_HOST = localhost - Host where your database is hosted.
  • TYPEORM_USERNAME = typeorm_user - Database username
  • TYPEORM_PASSWORD = typeorm_pass - Databae password
  • TYPEORM_DATABASE = db_typeorm - Database name
  • TYPEORM_PORT = 3306 - Database port (will use default port for connection type if no provided)
  • TYPEORM_SYNCHRONIZE = false - If set to true, TypeORM will effect changes to DB automatically. Do NOT use in production
  • TYPEORM_LOGGING = true - Defaults to false but very handy in dev time to see what TypeORM is doing
  • TYPEORM_ENTITIES = src/entity/**/*.ts - Where TypeORM should look for entity files
  • TYPEORM_MIGRATIONS = src/migration/**/*.ts - Where TypeORM should look for migrations to run
  • TYPEORM_MIGRATIONS_DIR = src/migration - Where TypeORM should store migration file outputs from npm run-migrations command
  • PORT=3000 - Express/Web server migrations

Migrations

In order to keep the database up to date with what is defined in the entities, you can use the TypeORM migrations tools.

As an example, lets say we have an entity of User like this:

import { Entity, Column, PrimaryGeneratedColumn, OneToMany } from "typeorm";

@Entity()
export class User {
  @PrimaryGeneratedColumn({ name: "id" })
  id: number;

  @Column({ name: "first_name" })
  firstName: string;

  @Column({ name: "last_name" })
  lastName: string;
}

We now change the entity by adding another field, createdAt as follows:

import { Entity, Column, PrimaryGeneratedColumn, OneToMany } from "typeorm";

@Entity("table_users")
export class User {
  @PrimaryGeneratedColumn({ name: "id" })
  id: number;

  @Column({ name: "first_name" })
  firstName: string;

  @Column({ name: "last_name" })
  lastName: string;

  @Column({
    name: created_at,
    type: "datetime",
    default: () => "CURRENT_TIMESTAMP",
    nullable: false,
  })
  createdAt: string;
}

For this entity to work with the database, a new column, created_at needs to be added to the table_users table.

The easy way is to turn syncronisation on using the TYPEORM_SYNCHRONIZE environment variable. This is NOT recommended in production environments as you might have unintended SQL being generated which could delete some of your data.

Instead, we can generate the migrations using npm run generate-migrations <branch-name> which will generate migrations that can be reverted if needed using CI/CD.

See: https://betterprogramming.pub/typeorm-migrations-explained-fdb4f27cb1b3