Not creating v7 uuids for ids

I'm using Ash 3.5 with AshPostgres. I have a Country resource with the following id attribute:

attributes do
  uuid_v7_primary_key :id

attributes do
  uuid_v7_primary_key :id

1. Create the table using Ash-generated migration 1a. Here's the generated extensions.json snapshot:

{
  "ash_functions_version": 5,
  "installed": [
    "ash-functions",
    "citext",
    "uuid-ossp", // Unrelated question.. how did this get here?
    "ash-uuid_v2"
  ]
}

{
  "ash_functions_version": 5,
  "installed": [
    "ash-functions",
    "citext",
    "uuid-ossp", // Unrelated question.. how did this get here?
    "ash-uuid_v2"
  ]
}

2. Populate the countries table via mix run priv/repo/seeds.exs See https://gist.github.com/dev-guy/7d8617b5da2d4207accf3365e88eb7fc for the seeder module. 3. Select * from countries 4. Notice that all of the id column values look like: 0f5f52a7-0ef0-445c-a59c-aacbcc56198a These are not v7 uuids. The number after the second hyphen is a 4, so they are v4 uuids. Have I not configured something correctly? Is this only a problem for seed data? 4a. Here is a uuid tester for reference:

case uuid do
  <<_::binary-size(14), ?4, _rest::binary>> -> :v4
  <<_::binary-size(14), ?7, _rest::binary>> -> :v7
  _ -> :other_or_invalid
end

case uuid do
  <<_::binary-size(14), ?4, _rest::binary>> -> :v4
  <<_::binary-size(14), ?7, _rest::binary>> -> :v7
  _ -> :other_or_invalid
end

Solution:

```elixir change fn changeset, _context -> if is_nil(Ash.Changeset.get_attribute(changeset, :id)) do Ash.Changeset.force_change_attribute(changeset, :id, Ash.UUID.generate()) # <- this is in your code you sent else...

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20 Replies

ZachDaniel•5mo ago

What is ash-uuid_v2? What do your seeds look like? I see it. Umm...pretty weird? I know it makes valid v7 uuids What does Ash.Resource.Info.attribute(Resource, :id) show? Can you share the whole resource?

TerrisOP•5mo ago

If you don't know what ash-uuid_v2 is, I'll remove it.

ZachDaniel•5mo ago

Well, hold on 😂 Just show me the resource first if you can

TerrisOP•5mo ago

I am using a base resource so it's not as simple as it sounds. https://gist.github.com/dev-guy/60c2355508fed8450e4b78fa61ff6690 https://gist.github.com/dev-guy/94d2767876d06fbe156f0dc5d987a190 Also, I don't know how ash-uuid_v2 got there. And I don't know how to remove it. Grepping my codebase doesn't show it except in the snapshot. BTW I'm also using ash-oban. OK, what I couldn't find is in repo.ex. I was following some (probably old) documentation and added uuid-ossp and AshUUID.PostgresExtension in my sleep. I'll remove those and see what happens.

  @impl true
  def installed_extensions do
    # Add extensions here, and the migration generator will install them.
    ["ash-functions", "citext", "uuid-ossp", AshUUID.PostgresExtension]
  end

  @impl true
  def installed_extensions do
    # Add extensions here, and the migration generator will install them.
    ["ash-functions", "citext", "uuid-ossp", AshUUID.PostgresExtension]
  end

It's still creating v7 uuids (at least when creating seed data) with the following repo/extensions snapshot

{
  "ash_functions_version": 5,
  "installed": [
    "ash-functions",
    "citext"
  ]
}

{
  "ash_functions_version": 5,
  "installed": [
    "ash-functions",
    "citext"
  ]
}

mix run priv/repo/seeds.exs outputs :

INSERT INTO "countries" ("id","name","flag","updated_at","created_at","iso_3166","slug") VALUES ($1,$2,$3,$4,$5,$6,$7) RETURNING "flag","iso_3166","updated_at","created_at","slug","name","id" ["bd9338d5-cfa5-4dbf-96f6-e1409cddf0a4", "Zambia", ":flag_zm:", ~U[2025-05-26 16:40:49.535660Z], ~U[2025-05-26 16:40:49.535660Z], "ZM", "zambia"]

INSERT INTO "countries" ("id","name","flag","updated_at","created_at","iso_3166","slug") VALUES ($1,$2,$3,$4,$5,$6,$7) RETURNING "flag","iso_3166","updated_at","created_at","slug","name","id" ["bd9338d5-cfa5-4dbf-96f6-e1409cddf0a4", "Zambia", ":flag_zm:", ~U[2025-05-26 16:40:49.535660Z], ~U[2025-05-26 16:40:49.535660Z], "ZM", "zambia"]

TerrisOP•5mo ago

Here is the Country resource. :id looks correct, but creating an instance using a changeset creates a v4 uuid.

Ash.Resource.Info.at...

TerrisOP•5mo ago

iex(3)> Ash.UUIDv7.generate
"01970d84-dba7-7e23-b205-06b6e2bacfcc"

iex(3)> Ash.UUIDv7.generate
"01970d84-dba7-7e23-b205-06b6e2bacfcc"

Ash.UUIDv7.generate works correctly. Apparently Ash is not actually calling it.

ZachDaniel•5mo ago

WHat does your database show for the underlying type? Did you change from uuuid to uuidv7 and forget to run mix ash.codegen?

TerrisOP•5mo ago

I've been running mix ash.codegen many times due to regenerating the repo/extensions snapshot . I also delete all of the migrations before that.

CREATE TABLE countries (
    id uuid DEFAULT uuid_generate_v7() PRIMARY KEY,

CREATE TABLE countries (
    id uuid DEFAULT uuid_generate_v7() PRIMARY KEY,

ZachDaniel•5mo ago

🤔 🤔 🤔 I don't understand how you could possibly be getting a regular uuid 😆

    create :create do
      accept [:name, :iso_3166, :flag]
      change HealthCompassDirectory.Resources.Changes.GenerateSlug

      change fn changeset, _context ->
        if is_nil(Ash.Changeset.get_attribute(changeset, :id)) do
          Ash.Changeset.force_change_attribute(changeset, :id, Ash.UUID.generate())
        else
          changeset
        end
      end
    end

    create :create do
      accept [:name, :iso_3166, :flag]
      change HealthCompassDirectory.Resources.Changes.GenerateSlug

      change fn changeset, _context ->
        if is_nil(Ash.Changeset.get_attribute(changeset, :id)) do
          Ash.Changeset.force_change_attribute(changeset, :id, Ash.UUID.generate())
        else
          changeset
        end
      end
    end

you're doing it 🙂

TerrisOP•5mo ago

The issue has to do with creating instances of Country resource. The id attribute is configured to call Ash.UUIDv7.generate, but creating a resource via a changeset is calling Ash.UUID.generate

ZachDaniel•5mo ago

🤔 On the create action you are calling you're setting the id to a uuid v4

Solution

ZachDaniel•5mo ago

change fn changeset, _context ->
  if is_nil(Ash.Changeset.get_attribute(changeset, :id)) do
    Ash.Changeset.force_change_attribute(changeset, :id, Ash.UUID.generate()) # <- this is in your code you sent
  else
    changeset
  end
end

change fn changeset, _context ->
  if is_nil(Ash.Changeset.get_attribute(changeset, :id)) do
    Ash.Changeset.force_change_attribute(changeset, :id, Ash.UUID.generate()) # <- this is in your code you sent
  else
    changeset
  end
end

TerrisOP•5mo ago

Yeah, I removed that.

ZachDaniel•5mo ago

and you recompiled and tried again? it won't fix the existing uuids in your database

TerrisOP•5mo ago

Right, I blow it away and start over. I will mix clean again.

ZachDaniel•5mo ago

I'm like...99% positive that its something in your code somehow setting these values to uuid v4s

TerrisOP•5mo ago

Sorry for wasting your time.

ZachDaniel•5mo ago

no need to apologize I'm not upset 😄

TerrisOP•5mo ago

I'm pretty sure if I hadn't fallen down this rabbit hole I would not have found out that user uuids were also v4, minor issue. Yep, rebuilding fixed it. Footgun.

TerrisOP•5mo ago

Oh, it was also useful to ask to get rid of the unnecessary extensions I added to the repo.

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Not creating v7 uuids for ids

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