mysql locking

snippet.rb

=begin
FOR UPDATE
- no one else can SELECT ... FOR UPDATE the row
- no one else can update/delete the row

LOCK IN SHARE MODE
- others may SELECT ... LOCK IN SHARE MODE
- no one else can update/delete the row
=end
require 'rubygems'
gem 'activerecord', '=2.3.5'
require 'active_record'

ActiveRecord::Base.establish_connection(
  :adapter  => "mysql",
  :host     => "localhost",
  :username => "root",
  :database => "syslitics_development"
)

class Account < ActiveRecord::Base
end

Account.transaction do
  a = Account.find(71, :lock => true)
  puts a.inspect
  sleep 10000
end

# this will block
#puts Account.find(71, :lock => true).inspect

# but this won't
#puts Account.find(71).inspect