After joining Remote and starting to find my way around our extensive data model, I quickly noticed how often I was repeating the Repo.preload/2 call to navigate through our data model.

The explicit preload strategy, instead of the automatic eager loading provided by other frameworks (like Rails' ActiveRecord, for example) serves as a deterrent to the unfortunately common problem of having N+1 queries popping up in Production.

With Ecto, you need to be deliberate upfront about whether you need the association loaded for you. Otherwise, you'll get this result when trying to reach out to the country.addresses.

#Ecto.Association.NotLoaded<association :addresses is not loaded> 

The following snippet shows that an association isn't loaded by default. Only after "preloading" it the association becomes "filled" with records coming from the DB.

André Albuquerque

Articles published on Remote by André Albuquerque