What is causing this ActiveRecord::ReadOnlyRecord error?

Question

This follows this prior question, which was answered. I actually discovered I could remove a join from that query, so now the working query is

start_cards =          


        

Answer 1

select('*') seems to fix this in Rails 3.2:

> Contact.select('*').joins(:slugs).where('slugs.slug' => 'the-slug').first.readonly?
=> false

Just to verify, omitting select('*') does produce a readonly record:

> Contact.joins(:slugs).where('slugs.slug' => 'the-slug').first.readonly?
=> true

Can't say I understand the rationale but at least it's a quick and clean workaround.