Getting auto-generated id without calling save


I have a bunch of models that are all related to each other through
various has_one, has_many, belongs_to relationships. I am trying to
create a set of these related objects when parsing through an XML
file, but would like to save the set as a whole through the use of
transactions, to cut down on the number of SQL COMMITs that are
called, as these are slowing down my app by a factor of 2 to 3
(compared to using transactions). However, as is not
being called until the transaction is processed, the foreign key
constraints for the relationships are failing. At first I was getting
the highest id value from the tables and using these to set the
values. The problem now is that I am using BackgrounDRb to do the
processing, and if several XML files come in in sequence, then two or
more of the BackgrounDRb workers are pulling the same id value from
the tables, as the transactions have not completed before the next
worker is generated.

Is there a way to get or set this auto-generated id value without
saving the object, so that I can continue using transactions without
causing this race condition?



Hi Simon,

You can wrap a set of rails commands in a single transaction by doing…

ActiveRecord::Base.transaction do


And it will only do one commit at the end.

Hope this helps,