Ruby-kai in Kyoto

Today is already too late, so just some notes. Need more research on "Transactions in Rails" (Takagi-san):

• Module ActiveRecord::Transactions::ClassMethods

Save and destroy are automatically wrapped in a transaction

• HowToUseTransactions

When you use the Transactions API, the system is really just using the underlying database SQL BEGIN...COMMIT. For MySQL, this means using InnoDB engine.

• Using transactions between two or more tables

A transaction acts on a single database connection. If you have multiple class-specific databases, the transaction will not protect interaction among them. One workaround is to begin a transaction on each class whose models you alter:

Account.transaction do
  User.transaction do
    yada_yada
  end
end

• Annoyances with ActiveRecord
• Transactional Fixtures in Ruby on Rails
• A better model for my Model

1. Switch all tables to InnoDB

alter table table_as engine=innodb

2. In the controller:

def insert_big_form
    TableA.transaction do
        ta = TableA.create({params[:table_a]})
        td = TableD.new({params[:table_d]})
        params[:table_c]["table_d"] = td
        ta.table_cs << TableC.new({:table_d => td, params[:table_c]})
        ta.table_b = TableB.new(params[:table_b])
        ta.save
    end
end

When shouldn't you use Rails? If you need to handle transactions across multiple databases. Rails/Ruby doesn't have two phase commit (yet).