ActiveRecord::ConnectionAdapters::ConnectionPool#with_connection usage

# Using ActiveRecord's trunk as of Oct 3, 2008, this fails with
#  active_record/connection_adapters/abstract/connection_pool.rb:158:in `checkin': undefined method `run_callbacks' for nil:NilClass (NoMethodError)

config = { 
  :adapter => "mysql",
  :host => "localhost", 
  :username => "root",
  :database => "jackgroundrb_development" 
}

ActiveRecord::Base.establish_connection(config)

class Promotion < ActiveRecord::Base; end

threads = []
50.times do |i|
  threads << Thread.new do
     puts "-----#{i}-----"
     ActiveRecord::Base.connection_pool.with_connection do |c|
       c.execute("select * from promotions where id = 1")
     end
     puts "+++++#{i}+++++"
  end
end

threads.each {|t| t.join}