TypeORM Basics — Series 2

Preview — 3 of 10 questions

What does this option do, and why must it stay off in production?

javascript

TypeOrmModule.forRoot({
  type: 'postgres',
  url: process.env.DATABASE_URL,
  entities: [Cat],
  synchronize: true,
});

AIt alters the database schema on every startup to match the entity definitions — convenient locally, but it can drop columns or tables whose entity definition changed, destroying data with no migration to review or roll back

BIt synchronises data between the primary database and its read replicas

CIt keeps entity instances in memory in sync with the database rows

DIt enables automatic retries for failed queries

Who sets these two values?

javascript

@Entity()
export class Cat {
  @PrimaryGeneratedColumn('uuid') id: string;
  @CreateDateColumn() createdAt: Date;
  @UpdateDateColumn() updatedAt: Date;
}

AThe application must assign them before calling save()

BA database trigger that TypeORM installs during the first migration

CTypeORM manages them automatically — createdAt is set on insert and updatedAt is refreshed on every update, with no application code involved

DThey are computed on read from the transaction log

What does each call do?

javascript

const cat = this.repo.create({ name: 'Bombay' });
await this.repo.save(cat);

Acreate() inserts the row and save() commits the surrounding transaction

BBoth write to the database; create() inserts and save() updates

Ccreate() validates the data against the entity's decorators and save() persists it

Dcreate() only builds an entity instance in memory — no SQL is issued — while save() is the call that inserts (or updates) the row

Answer all 10 questions (7 more), see explanations for every answer, and track your score.