Does rails do a rollback if I use begin...rescue?

Question

I'd like to add a begin...rescue block to one of my controllers create method, in order to log better info and construct the correct error message to return to the client. Does the rescue in any way 'interrupt' the rollback process?

I'm assuming rails automatically does a rollback. When does it happen? Has it already happened by the time I get in the rescue clause?

I'm using mySQL on Dreamhost and I think they use innoDB.

Answer 1

Just using begin...rescue isn't enough to rollback a transaction. You need to use:

ModelName.transaction do 
end

This is done explicitely on a call to save, so that all of your callbacks are executed together. What exceptions are you catching in your rescue block? What are you responding to? What kind of errors?

Answer 2

Here's the official documentation on transactions in Rails:

http://api.rubyonrails.org/classes/ActiveRecord/Transactions/ClassMethods.html

It may not be obvious from the docs, but the way to trigger a rollback is to raise ActiveRecord::Rollback, like this:

Model.transaction do
    model1.save!
    model2.save!

    # Check one more thing
    if something_is_wrong
        raise ActiveRecord::Rollback
    end
end

# Even if the transaction was rolled back via ActiveRecord::Rollback,
# execution will resume here, after the transaction block, which effectively
# catches the Rollback exception.