Migration script places unique index below relationships they're needed for

Describe the bug Migration produces unique indexes too late in the script for relationships that depend on them.

To Reproduce I've got a recource that is a many-to-many table. I also need it to contain items as a linked list. So I created a unique constraint on the id for the foreign key. The framework generates a migration, but creates the line to add the unique constraint AFTER the alter table statement that creates the foreign key to self. So the migration fails unless I move the create unique index statement above the alter table.

defmodule MyProj.TemplateManager.TemplatePhase do use Ash.Resource, datalayer: AshPostgres.DataLayer

postgres do
  table "templatephase"
  repo MyProj.Repo
end

attributes do
  uuid_primary_key :id
  attribute :name, :string do
    allow_nil? false
  end
end

identities do
  identity :id, [:id]
end

relationships do
  belongs_to :template, MyProj.TemplateManager.Template, primary_key?: true, allow_nil?: false
  belongs_to :phase, MyProj.TemplateManager.Phase, primary_key?: true, allow_nil?: false
  belongs_to :template_phase, __MODULE do
    source_attribute :follows
    destination_attribute :id
    attribute_writable? true
    allow_nil? true
  end
end

actions do
  defaults [:create, :read, :update]
end

end

Which produces the migration file with the relevant parts in this order:

alter table(:template_phase) do
  modify :phase_id,
         references(:phase,
           column: :id,
           name: "template_phase_phase_id_fkey",
           type: :uuid,
           prefix: "public"
         )

  modify :follows,
         references(:template_phase,
           column: :id,
           name: "template_phase_follows_fkey",
           type: :uuid,
           prefix: "public"
         )
end

create unique_index(:template_phase, [:id], name: "template_phase_id_index")

Expected behavior If I move the bottom line to the top of this exerpt, the migration succeeds and I get this DB structure (otherwise the migrate command fails because the unique constraint has yet to be applied):

Table "public.template_phase" Column | Type | Collation | Nullable | Default -------------+------+-----------+----------+-------------------- id | uuid | | not null | uuid_generate_v4() name | text | | not null | template_id | uuid | | not null | phase_id | uuid | | not null | follows | uuid | | | Indexes: "template_phase_pkey" PRIMARY KEY, btree (id, template_id, phase_id) "template_phase_id_index" UNIQUE, btree (id) Foreign-key constraints: "template_phase_follows_fkey" FOREIGN KEY (follows) REFERENCES template_phase(id) "template_phase_phase_id_fkey" FOREIGN KEY (phase_id) REFERENCES phase(id) "template_phase_template_id_fkey" FOREIGN KEY (template_id) REFERENCES template(id) Referenced by: TABLE "template_phase" CONSTRAINT "template_phase_follows_fkey" FOREIGN KEY (follows) REFERENCES template_phase(id) (edited) Jump general

** Runtime

• Elixir version: 1.16.2
• Erlang version: 26
• OS: Ubuntu 22
• Ash version: 2.20.1
• Ash Postgres: 1.5.17

Additional context Add any other context about the problem here.