update a column without changing updated_at

Question

This may sound like an odd request, however, I have am using impressionist, and using a cached hit column. I am also updating another column everytime it gets a hit, which is a separate calculation.

I don't want to update updated_at at this time, is there a way to skip that?

if impressionist(@topic, "message...", :unique => [:session_hash])
  @topic.increment(:exp, 1).save
end

Thanks

Answer 1

The update_columns method from ActiveRecord::Persistence will do what you want.

Answer 2

In addition to disabling timestamps for an entire class (which isn't thread safe), you can disable timestamps for an individual instance:

@topic.record_timestamps = false
@topic.increment(:exp, 1).save

This instance will not create or update timestamps until timestamps are re-enabled for it. This only affects this particular instance, other instances (even if they refer to the same row in the database) are not affected.