Question

I have two models – Topic and ContentItems.

A topic has_many content_items but a topic can be created without any pre-existing content_items.

Does anyone know how I can select all Topics with at least one content_item without using a counter cache?

currently I’m doing something like:

Topic.joins(:content_items).uniq

but that handles it in memory so if I can’t chain a limit or order off of it i.e. I can’t do

Topic.joins(:content_items).uniq.limit(10).order("created_at DESC")

Counter cache is a possible long term option but it’s a bit larger of a change than I’d like to make right now unless there are no better solutions.

Thanks all

Answer 1

You can try this

Topic.joins(:content_items).select("DISTINCT topics.*")

OR

Topic.include(:content_items).where("content_items.id IS NULL")