Ash FrameworkAF
Ash Framework•3y ago•
30 replies
Korbin

Differences between UUID primary keys in Ecto vs Ash

As far as I can tell, the Ash Resource special attribute uuid_primary_key unwraps into:
attribute :id, :uuid do
  writeable? false
  default &Ash.UUID.generate/0
  primary_key? true
  allow_nil? false
end


Ash.UUID.generate/0 seems to be a passthrough to Ecto.UUID.generate(). What I found unexpected was the migration files.

Echo's migration file looks like:
...
def change do
  create table(:posts, primary_key: false) do
    add :id, :binary_id, primary_key: true
    ...
  end
end


Ash's migration file looks like:
def up do
  create table(:posts, primary_key: false) do
    add :id, :uuid, null: false, default: fragment("uuid_generate_v4()"), primary_key: true
    ...
  end
end


I'm not entirely sure if the functionality will all be the same at the end of the day. Reading docs and source code, it seems like Postgrex treats :binary, :binary_id, and :uuid similarly when ran by Ecto SQL, but I'm not sure.

The most surprising is the :default option in Ash's implementation. It hard-codes a Postgres DB function as a default value even though :primary_key option is set (which I think inherently makes the field non-nullable in most databases.

The reason I'm worried about it is because I'm interested in using UUIDv7 for my PKs. That function may never run if generating UUIDs in Elixir-land, but it seems off to be there.
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