ActiveRecord fails to update without a pause

Hi there,
I’m having a strange issue with active record in 2.3.2 development env
whereby an update_ attribute within a loop only gets written to the db
if I write (anything) to the logfile, or set a sleep of somewhere
between 0.5 and 1 second.

The function is a remotely called drag and drop list sorter:

def sort
i = 1
params[:cv].each {
|id|
if cv_type = current_user.cv_types.find(id)
if cv_type.update_attribute(:position, i)
sleep 1 # if I remove this it doesn’t work any more
i = i+1
end
end
}
render :nothing => true
end

and from the logfile without the sleep command:

CvType Load (0.2ms) SELECT * FROM cv_types WHERE
(cv_types.id = 5 AND (cv_types.user_id = 1)) ORDER BY position
SQL (0.1ms) BEGIN
SQL (0.1ms) COMMIT
CvType Load (0.4ms) SELECT * FROM cv_types WHERE
(cv_types.id = 4 AND (cv_types.user_id = 1)) ORDER BY position
SQL (0.1ms) BEGIN
SQL (0.1ms) COMMIT

and then with the sleep command:

CvType Load (0.5ms) SELECT * FROM cv_types WHERE
(cv_types.id = 4 AND (cv_types.user_id = 1)) ORDER BY position
SQL (0.1ms) BEGIN
CvType Update (0.2ms) UPDATE cv_types SET position = 1 WHERE
id = 4
SQL (0.5ms) COMMIT
CvType Load (0.4ms) SELECT * FROM cv_types WHERE
(cv_types.id = 5 AND (cv_types.user_id = 1)) ORDER BY position
SQL (0.1ms) BEGIN
CvType Update (0.2ms) UPDATE cv_types SET position = 2 WHERE
id = 5
SQL (0.6ms) COMMIT

Surely that isn’t normal?
I don’t mind writing to the logfile, but it seems that something else
is afoot. and I can’t think what.

Any insight would be very helpful.
thanks,
dorian