Use Ecto.Multi to insert all hit data in a single

[nelsonic]

At present we are using 4 queries to insert a single hit.
This works "OK" and is "fast enough" but we can probably do better ...

Thankfully @katbow wrote this helpful guide:
https://github.com/dwyl/learn-phoenix-framework/blob/master/ecto-multi.md
So it should be pretty straightforward to refactor.

Todo

• Refactor the insert_hit function (and supporting functions) to use Ecto.Multi

[nelsonic]

I don't think using Ecto.Multi is possible because the foreign keys of users, useragents and repositories are required for hits ...
see: https://github.com/dwyl/hits#view-the-entity-relationship-er-diagram
But I would be very happy if someone could show us how it can be done.

[katbow]

You can use the result of previous operations in a Multi.

Multi.new
|> Multi.insert_or_update(:user_agent, user_agent_params)
|> Multi.insert_or_update(:user, user_params)
|> Multi.run(:repository, fn _repo, %{user: user} -> 
  # something that inserts/updates Repository with the user and returns {:ok, value} or {:error, value}
|> Multi.run(:hit, fn _repo, %{user_agent: user_agent, repository: repository} ->
  # something that inserts/updates Hit with the user agent & repository and returns {:ok, value} or {:error, value}

The multi tracks all the changes so far. You can see it in Healthlocker where the multi is accessed directly.

Check out run/3 & run/5, and basic usage with Result of a previous operation section.

[nelsonic]

@katbow nice! Thanks for sharing! ☀️