ActiveRecord Cross-DB transactions

gistfile1.rb

# AR transactions wrap a block of code, issuing a rollback if any errors are raised.
#
#(note: this gist makes use of SecondBase https://github.com/customink/secondbase)
require 'secondbase/model'

AR = ActiveRecord::Base
SB = SecondBase::Base

# The transaction returns the return value of the block
AR.transaction { 14 } #=> 14

# Errors are propagated...
AR.transaction { raise } #=> RuntimeError

# ...except ActiveRecord::Rollback errors
AR.transaction { raise ActiveRecord::Rollback } #=> nil

# --
# What does this mean cross-db??
# --

# We can nest transactions...
AR.transaction do
  SB.transaction do
    14
  end
end #=> 14

# ...as long as we mind our errors!
AR.transaction do
  SB.transaction do
    ARModel.save
    
    if SBModel.new.save
      raise ActiveRecord::RecordNotSaved #=> Error will be propagated, and both AR and SB rollbacks issues
    end
  end
end

AR.transaction do
  SB.transaction do
    ARModel.save
    
    if !SBModel.new.save
      raise ActiveRecord::Rollback #=> Error will NOT be propagated, only SB rollback issued
    end
  end #=> nil
end #=> nil, even though the AR record has been saved!