TypeORM OneToMany relation doesn't add entry to the array when it is created

I am trying to create two entities - Assignment and Lesson. Each Lesson can have multiple Assignments and each Assignment can be part of one Lesson. When I create a Lesson with Assignments in it, the Assignemnts get created, they are added to the assignments array and everything works.

When I create a Lesson and then try to add a new Assignment to it, the Assignment is created, it is linked to the correct Lesson but the assignments field in the Lesson is not updated.

Is this how it is supposed to work or is there any way to update the assignments array in Lesson?

Below is my code. I am using a sqlite in-memory database

Assignment.ts

import { Entity, Column, PrimaryGeneratedColumn, TableInheritance, ManyToOne, JoinColumn } from 'typeorm';
import { Lesson } from './Lesson';

@Entity()
@TableInheritance({ column: { type: 'varchar', name: 'type' } })
export abstract class Assignment {
    @PrimaryGeneratedColumn()
    id: number;

    @Column()
    name: string;

    @ManyToOne(() => Lesson, (lesson) => lesson.assignments, { eager: true })
    @Column('json')
    lesson: Lesson;
}

Lesson.ts

import { Entity, Column, PrimaryGeneratedColumn, OneToMany } from 'typeorm';
import { Assignment } from './Assignment';

@Entity()
export class Lesson {
    @PrimaryGeneratedColumn()
    id: number;

    @Column()
    name: string;

    @OneToMany(() => Assignment, (assignment) => assignment.lesson, { cascade: true })
    @Column('json')
    assignments: Assignment[];
}

I have tried adding @JoinColumn() to the @ManyToOne relation but nothing changed

You should probably add your code that shows how you are accessing your data... but Ill take a stab:

typically you'll add a lesson to an assignment as follows:

const lesson = await Lesson.findOne({where:{id:1},relations:['assignments]})
const assignment = await Assignment.findOne({where:{id:1}}
assignment.lesson = assignment
await assignment.save()
// at this point lesson wont have your new assignment
// you could just add it to the lesson.assignments array
lesson.assignments.push(assignment)
// or you could re-read from the db
const lessonAfterAdd = 
await Lesson.findOne({where:{id:1},relations['assignments]})

The solution was to remove the @Column annotation from both of the fields - assignments and lesson.

I could also add a filed lessonId: number with the @Column annotation to store the lesson id in the Assignment.