How to create a trigger in nestjs with typeorm?

Question

Is there any way to create a trigger in nestjs/typeorm. This trigger should

1. Auto-increment a column whenever that row is updated
2. Work even when working directly in mysql database

Answer 1

Don't know whether @nestjs/typeorm has that functionality or not but the core typeorm package do support triggers out of the box.

You can try something like this using the core typeorm package :

@EventSubscriber()
export class PostSubscriber implements EntitySubscriberInterface {
 
    /**
     * Called before entity update.
     */
    beforeUpdate(event: UpdateEvent<any>) {
        console.log(`BEFORE ENTITY UPDATED: `, event.entity)
        manager.update(YourEntity, { yourColumn : value })
    }

    /**
     * Called after entity update.
     */
    afterUpdate(event: UpdateEvent<any>) {
        console.log(`AFTER ENTITY UPDATED: `, event.entity)
    }

   
}

The event object contains :

• dataSource: DataSource - DataSource used in the event.
• queryRunner: QueryRunner - QueryRunner used in the event transaction.
• manager: EntityManager - EntityManager used in the event transaction.

Note: All database operations in the subscribed event listeners should be performed using the event object's queryRunner or manager instance.

You can further read about this at https://typeorm.io/listeners-and-subscribers#what-is-a-subscriber.

Do let me know if this solves your issue.

Answer 2

I fixed this issue by explicitly creating triggers in mysql.