Question

The goal: when a User is deleted, all entries for a user in UserCategory should be deleted as well.

The schema:

User:
  actAs: { Timestampable: ~ }
  columns:
    first_name: { type: string(255) }
    name: { type: string(255) }
    company: { type: string(255) }
    email: { type: string(255) }
    phone: { type: string(255) }
    language_id: { type: integer, notnull: true }
    token: { type: string(255) }
    activated: { type: boolean, default: false }
  relations:
    Categories:
       class: Category
       local: user_id
       foreign: category_id
       refClass: UserCategory
       type: many

UserCategory:
  actAs: { Timestampable: ~ }
  columns:
    user_id: { type: integer, notnull: true }
    category_id:      { type: integer, notnull: true }

Category:
  actAs: { Timestampable: ~ }
  columns:
    language_id:  { type: integer, notnull: true }
    name: { type: string(255), notnull: true, unique: false }
    revision: { type: integer, notnull: false }
    icon:     { type: string(255) }
  relations:
    User:
       class: User
       local: category_id
       foreign: user_id
       refClass: UserCategory
       type: many

What happens:

SQLSTATE[23000]: Integrity constraint violation: 1451 Cannot delete or update a parent row: a foreign key constraint fails (testtable.user_category, CONSTRAINT user_category_user_id_user_id FOREIGN KEY (user_id) REFERENCES user (id))

Answer 1

Like greg0ire said, defining a cascade for UserCategory did the job. It missed the relations block entirely:

UserCategory:
  actAs: { Timestampable: ~ }
  columns:
    user_id: { type: integer, notnull: true }
    category_id:      { type: integer, notnull: true }
  relations:
    User: {onDelete: CASCADE, local: user_id, foreign: id, foreignAlias: Users}
    Category: {onDelete: CASCADE, local: category_id, foreign: id, foreignAlias: Categories}