I am deeply confused by what’s going on.
- I have two entities –
Sprint
andActivityStereotype
. The former is the “parent,” meaning, sprints can have zero or more activity stereotypes. When deleting a sprint its activity stereotypes should also be deleted. - It works fine in
iex -S mix
interactively. See below. - But when I try to compile / run a unit test, I get a bizarre 42P07 “duplicate table” error.
- But I’m also a little bit confused about Ash architecture and how relationships (and specifically, cascading relationships in Postgres) are supposed to be handled.
Like I said, all is well interactively:
iex(6)> {:ok, s2} = COE.Walk.Sprint.create("meeting", ~D[2011-01-01], ~D[2011-01-15])
{:ok, #COE.Walk.Sprint...}
iex(7)> {:ok, a2} = COE.Walk.ActivityStereotype.add("meetings", s2.id)
{:ok, #COE.Walk.ActivityStereotype...}
iex(8)> s2
iex(9)> |> COE.Walk.destroy!()
:ok
My journey thus far…
I had assumed on_delete:
was handled by Ash internally when using relationships with not null constraints. For example:
# activity_stereotype.ex
relationships do
# Activity stereotypes belonog to a sprint, so this is a required relationship
belongs_to :sprint, COE.Walk.Sprint do
attribute_writable? true
allow_nil? false
end
end
# sprint.ex
relationships do
has_many :activity_stereotype, COE.Walk.ActivityStereotype
end
Apparently not, which is fine. At this stage, deleting a sprint results in an error that “would leave records behind” (which I interpret to mean, “you can’t do that, it would leave an orphan activity stereotype”). Makes sense. Begin quest to figure out how to configure cascading deletes.
In trying to figure out how to set up a cascading delete, I found a relevant page on References in Ash Postgres. It’s lacks some context and complete examples, but… it seems to be saying I should add a new references
block to my postgres
block, so I added it here (footnote; kind of ugly that I now have two references
in my module… seems redundant but meh)…
# activity_stereotype.ex
postgres do
table "stereotypes"
repo BossSite.Repo
references do
reference :sprint, on_delete: :delete, on_update: :update, name: "activity_stereotype_sprint_fkey"
end
end
And rebuilt the database (it’s young, no need for migrations). Data rebuild is fine. All looks good.
Compile. Run unit tests.
Now I’m getting an error during unit tests that I really don’t understand:
% mix test test/coe/activity_stereotype_test.exs
Compiling 2 files (.ex)
** (Postgrex.Error) ERROR 42P07 (duplicate_table) relation "stereotypes" already exists
(ecto_sql 3.11.0) lib/ecto/adapters/sql.ex:1054: Ecto.Adapters.SQL.raise_sql_call_error/1
(elixir 1.15.7) lib/enum.ex:1693: Enum."-map/2-lists^map/1-1-"/2
(ecto_sql 3.11.0) lib/ecto/adapters/sql.ex:1161: Ecto.Adapters.SQL.execute_ddl/4
(ecto_sql 3.11.0) lib/ecto/migration/runner.ex:348: Ecto.Migration.Runner.log_and_execute_ddl/3
(elixir 1.15.7) lib/enum.ex:1693: Enum."-map/2-lists^map/1-1-"/2
(ecto_sql 3.11.0) lib/ecto/migration/runner.ex:311: Ecto.Migration.Runner.perform_operation/3
(stdlib 5.0.2) timer.erl:270: :timer.tc/2
(ecto_sql 3.11.0) lib/ecto/migration/runner.ex:25: Ecto.Migration.Runner.run/8
I checked the Postgres instance (and the migrations)… there is only one stereotypes
table. I’m assuming this means there is some kind of duplicate reference being generated in the dynamic SQL somewhere… but… no idea. Drop into iex
and play around to see if I can figure out what’s up:
It works just fine. WTH… (ノಠ益ಠ)ノ彡┻━┻
A few key points:
- I’m getting the error at unit test compile (not when running migrations / creating the database; the database is created – this happens during unit testing only)
- I’ve checked the SQL and it looks good to me, although my SQL is rusty – including it below just in case – anyhow, it works great in
iex
- After reading this post I’m more confused about Ash Postgres, relationships, and the idiomatic approach to cascading constraints… and am wondering if I should be adding
on_missing: destroy
to amanage_relationships
call – because mostly, it sounds like @zachdaniel is saying “that should have been managed by Ash core anyhow.” I think. But this is just tangential and doesn’t really answer WTH is going on with my unit tests…!
For thoroughness… the migration:
# database migration
def up do
create table(:stereotypes, primary_key: false) do
add :id, :uuid, null: false, default: fragment("uuid_generate_v4()"), primary_key: true
add :name, :text, null: false
add :allowed_types, {:array, :text}, null: false
add :default_type, :text, null: false, default: "value_add"
add :sprint_id, :uuid, null: false
end
create table(:sprints, primary_key: false) do
add :id, :uuid, null: false, default: fragment("uuid_generate_v4()"), primary_key: true
end
alter table(:stereotypes) do
modify :sprint_id,
references(:sprints,
column: :id,
name: "activity_stereotype_sprint_fkey",
type: :uuid,
prefix: "public",
on_delete: :delete_all,
on_update: :update_all
)
end
alter table(:sprints) do
add :name, :text, null: false
add :start_date, :date, null: false
add :end_date, :date, null: false
end
As always thanks for your help!