Comments on: counter_cache as an optimization step

By: mattenat

mattenat — Wed, 07 Oct 2009 18:29:07 +0000

Thanks Rain. Updated the code in the post, accordingly!

By: Rain

Rain — Tue, 06 Oct 2009 09:40:50 +0000

You forgot the scenario about destroying images, it will not update the counter unless you set
has_many :images_tags, :dependent => :destroy in Image model

but it will require ImagesTag model has a primary key, so you have to add a primary key for it in the migration script.

By: Jim

Jim — Thu, 01 Oct 2009 21:10:36 +0000

It’s even older than that: it’s on page 361 of the 2d edition Agile Web Development from PragProg, which makes it pre-Rails 1.2.3 IIRC.

That book is totally worth a skim cover-to-cover so you can have many of those “don’t I remember that one thing …” moments. It won’t replace keeping up with Edge Rails (or just reading the code you’re using ;), but it’s a good backup.