I love Erlang/Elixir and want to use it more, but I just don’t have any good use cases for it! I don’t often make big concurrent back ends - maybe REST APIs, but that didn’t seem easy last time I tried.
Imo this is actually much better than an orm because it really hits home that the data in memory are stale as soon as you receive them because database transactions are explicit, and not hidden behind getters and setters.
ORMs can get you into trouble because they try really hard to hide the problem of distributed state and sources of truth.
It has this cute macro-based syntax, and that seems to inform even the "functional" API as well. Yet when you I wanted to do something just a bit more advanced like joining on an association whose name I don't know in advance (or, say, want to parameterize the function with), I had to resort to writing a macro myself and then eval-ing it an runtime.
Well, take the numerous articles extolling the virtues of Sequel, or DataMapper, or, related to the current discussion, Ecto itself. Like how expressive this stuff is. And how ActiveRecord creates a too huge API surface on models, and that that leads to bad design, etcetera. Now to mention the callbacks, which are admittedly problematic.
But then I try those aforementioned libs and see sharp corners like terrible argument validations (in case of Sequel) which lead to silently failing code, or actual hard limitations on what I can ask Ecto to do without resorting to meta-programming.
> I also haven't ever found a good replacement for AR migrations
IME, both Sequel and Ecto migrations are fairly serviceable. But neither provides the schema dumping feature that AR has. Which is pretty handy.
The first part is your schema. It defines an Elixir struct that is your domain model of your data.
The second idea/part is the concept of a changeset. It represents a change you'd like to make to the data store, but haven't yet. These are composable, so you can bundle a bunch of changes into a single, atomic unit, which you then send to your repo. If any part fails, then the whole thing fails, no changes are made to the persisted data.
The last thing is migrations, which strictly speaking are optional, but a huge convience. They define how you'd like your database to be structured. The cool thing about them is that they define rollback operations automatically.
Once Ecto "clicks", it really becomes a strong selling point to the language as a whole. It makes working with persisted data super easy.