Ecto Migration On Update Cascade

Phoenix Forum Questions / Help
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1

Hi!

When setting up a migration, I need to specify the foreign key constraint, ON UPDATE -> CASCADE (MySQL). I’ve read the documentation, whoever there is only mention to the on_delete constraint. Using, on_replace, or on_cascade doesn’t work. Is this method implemented?

  def change do
    create table(:user_exam) do
      add :user_id, references(:user, on_delete: :nothing, on_cascade: :update), null: false
      add :exam_id, references(:exam, on_delete: :nothing, on_cascade: :update), null: false
      add :level, :integer, null: false

      timestamps()
    end

    create unique_index(:user_exam, [:user_id, :exam_id])
    create index(:user_exam, [:user_id])
    create index(:user_exam, [:exam_id])
  end
2

Doesn’t the option on_update: :update_all do what you want?
https://hexdocs.pm/ecto_sql/Ecto.Migration.html#references/2

1 Like
3

@thojanssens1 Thanks! I couldn’t find it.

4

If I understand correctly, if the referenced ID is updated, you want all references to it to update as well.

Can I ask you how an ID can ever change?

5

In most cases, this is not necessary. But we had cases in which we need to update an ID for an specific table, in order to comply with a client