broken_repo.ex

alias SchedWeb.Repo

Ecto.Adapters.SQL.query(Repo, "CREATE TABLE foos (id serial primary key)", [])
Ecto.Adapters.SQL.query(Repo, "CREATE TABLE bars (id serial primary key, foo_id integer not null references foos)", [])
Ecto.Adapters.SQL.query(Repo, "create unique index index_bars_on_foo_id ON bars(foo_id)", [])

defmodule Foo do
  use Ecto.Schema

  schema "foos" do
    has_many :bars, Bar
  end
end

defmodule Bar do
  use Ecto.Schema
  import Ecto
  import Ecto.Changeset

  schema "bars" do
    belongs_to :foo, Foo
  end

  def create(foo_id) do
    %__MODULE__{}
    |> change(foo_id: foo_id)
    |> unique_constraint(:foo_id, name: :index_bars_on_foo_id)
  end
end


# Test Run:

import Ecto.Query
Repo.transaction(fn ->
  foo = %Foo{} |> Repo.insert!()
  Bar.create(foo.id) |> Repo.insert!()
  
  try do
    Bar.create(foo.id) |> Repo.insert!()
  rescue
    err in [Ecto.InvalidChangesetError] ->
      IO.inspect err
  end

  # Repo connection is completely busted here
  (from b in Bar, select: count(b.id)) |> Repo.one!  #=> ** (exit) exited in: Ecto.Adapters.SQL.query(SchedWeb.Repo, "SELECT count(b0.\"id\") FROM \"bars\" AS b0", [], []) ** (EXIT) :noconnect
end)