Rene Veerman wrote:
i haven't had the pleasure yet of writing for sites that generate so many
hits/sec that
they'd update the max value of any table at exactly the same time.
i usually ask for the max value about 2 milliseconds before doing the
insert.
And if the insert fails, i can auto-retry via a wrapper function after
sleep(rand(1,3));
I dare say i could work this way at facebook <g> (not that i really want to,
happy with where i am)
This is a race condition... all you need are two hits per day... one
from person A and one from person B. If they happen within short enough
temporal proximity then the race is on.
Now... a big fat lock around the table before the request for max ID and
the insert query ought to mitigate your issue. Although I wouldn't call
my function getMaxId() I would call it getNextId() :)
Cheers,
Rob.
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