Rep.update returning ok with if: :exists while no record exists and Cassandrax returns false applied

[erobit]

BTW great job with this package!

I'm having issues with performing Repo.update(user, if: :exists) and having {:ok, %User{...}} returned even though the record does not exist and no updates are applied in Cassandra.

As you can see in the adapter prepare_result method, false/applied returning :ok

cassandra_ecto/lib/cassandra_ecto/adapter.ex

Line 294 in 99c839d

{[false | row], [_ | cols], :nothing} -> {:ok, Enum.zip(cols, row)}

It's also not clear from the update function signature how to return an :error
https://github.com/elixir-ecto/ecto/blob/v2.1.3/lib/ecto/adapter.ex#L172

Basically the changeset values are being applied instead of an :error being returned. Do you have some insight?

[vintikzzz]

Hi, it is quite tricky situation right here. According to https://github.com/elixir-ecto/ecto/blob/v2.1.3/lib/ecto/adapter.ex#L172 it is possible to return {:invalid, constraints}, but while doing Repo.update(user, if: :exists) we don't really hit any constraint.

I can suggest only to use Repo.update!(user, if: :exists) instead for right now.

Can you propose better solution?