q1 = Question.find(1) q2 = Question.find(1) Now, we find q1.__id__ != q2.__id__. It appears the two aliases are not kept in sync: q1.name => 'old name' q2.name = 'new name' q2.save! q1.name => 'old name' q2.name => 'new name' q1.reload q1.name => 'new name' Even worse, is this fun: q1.destroy q2.name = 'third name' q2.save! That actually runs; ActiveRecord happily updates all 0 rows that match (let's hope IDs can never be re-used, or that could have just updated the wrong row) Finally, q2.reload ActiveRecord::RecordNotFound: Couldn't find Question with ID=1 Why does ActiveRecord return two objects both representing a single row in the database?
on 2006-03-07 06:33
on 2006-03-07 09:07
This is correct. Rails doesn't use IdentityMap pattern (in terms of PoEAA). You should be aware of that when you develop with Rails. Kent
on 2006-03-07 22:07
Kent S. wrote: > This is correct. Rails doesn't use IdentityMap pattern (in terms of > PoEAA). You should be aware of that when you develop with Rails. Is .save! working on a record that (no longer) exists at least a bug? Especially on databases that return the number of effected rows (at least Pg and MySQL), this should be really easy to detect.
on 2006-03-08 01:47
That particular case I'd recommend to handle with database transactions and an appropriate isolation level set. Also you should look at the AR::Locking facility at http://api.rubyonrails.org/classes/ActiveRecord/Locking.html Kent.