Find or Create in Ecto

find_or_create.exs

# two different ways to implement a find_or_create for Ecto

find_or_create_user = fn user ->
  case Repo.all(from u in users, where: u.id == ^user.id and u.email == ^user.email) do
    [] ->
      %User{}
      |> User.changeset(user)
      |> Repo.insert!()
    _ ->
      IO.puts "Already inserted"
  end
end

def find_or_create(user) do
  query = from u in users,
          where: u.uid == ^user.uid
  if !Repo.one(query)  do
    Repo.insert(user)
  end
  Repo.one(query)
end

@protestContent this is better but still not the exactly correct behavior. At least on Postgres the serial autoincrement id increases even with on_conflict: :nothing, so with enough find_or_create calls this will needlessly increase autoincrement IDs by quite a bit.

@wyozi good point, I didn't realize that. Still better than a race condition imo. I wonder what the postgres community recommends in cases like this.