On Mar 2, 9:24 am, MaD <[email protected]> wrote:
> vendor/rails/activerecord/lib/active_record/locking/pessimistic:
> # Pass <tt>:lock => true</tt> to ActiveRecord::Base.find to obtain
> an exclusive
That's a row lock :-) If you want a table lock you need to run the
appropriate sql statement for your database by hand.
Fred
> # lock on the selected rows:
> # # select * from accounts where id=1 for update
> # Account.find(1, :lock => true)
> #
> # Pass <tt>:lock => 'some locking clause'</tt> to give a database-
> specific locking clause
> # of your own such as 'LOCK IN SHARE MODE' or 'FOR UPDATE NOWAIT'.
> #
> # Example:
> # Account.transaction do
> # # select * from accounts where name = 'shugo' limit 1 for
> update
> # shugo = Account.find(:first, :conditions => "name =
> 'shugo'", :lock => true)
> # yuko = Account.find(:first, :conditions => "name =
> 'yuko'", :lock => true)
> # shugo.balance -= 100
> # shugo.save!
> # yuko.balance += 100
> # yuko.save!
> # end
> #
> # You can also use ActiveRecord::Base#lock! method to lock one
> record by id.
> # This may be better if you don't need to lock every row. Example:
> # Account.transaction do
> # # select * from accounts where ...
> # accounts = Account.find(:all, :conditions => ...)
> # account1 = accounts.detect { |account| ... }
> # account2 = accounts.detect { |account| ... }
> # # select * from accounts where id=? for update
> # account1.lock!
> # account2.lock!
> # account1.balance -= 100
> # account1.save!
> # account2.balance += 100
> # account2.save!
> # end
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