I wouldn't expect it to lock the database (though someone with more
database expertise should address that). I /would/ expect it to consume
significant CPU. If you're on UNIX, you could address this issue by
making your process 'nice':
http://docs.python.org/library/os.html#os.nice The nicer a process
(higher the value), the less CPU it will hog. IIRC, nice values default
to 0 for processes and range from -20 (biggest CPU usage) to +20
(smallest CPU usage).
_Nik
On 11/22/2011 2:37 PM, Nan wrote:
> Hi folks --
>
> I need to run a fairly CPU-intensive calculation nightly over a
> dataset that's already large and growing quickly. I'm planning to run
> this via a cron job, but would like to make sure that it neither eats
> up the entire CPU nor locks the database, so that my site can continue
> functioning in the meantime. The rough outline of what it needs to do
> is as follows:
>
> class OtherThing(models.Model):
> anotherthing = models.ManyToManyField(Whatever)
> ...
>
> class Thing(models.Model):
> other_things = models.ManyToManyField(OtherThing,
> through='SomethingElse')
> ...
>
> for thing in Thing.objects.select_related('other_things',
> 'other_things__anotherthing__etc'):
> calculated = calculation_on_thing_and_its_otherthings(thing) #
> this mainly involves serialization to a great depth
> thing.calculated_data = calculated
> thing.save()
>
> Will the above approach lock the database for a while or eat tons of
> CPU? Any suggestions? I'm using Django 1.2, btw.
>
> Thanks,
> -Nan
>
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