Has anyone else noticed performance issues using Django's F() object? I am running Windows XP SP3 and developing against the Django trunk. A snippet of the models I'm using and the query I'm building are below. When I have the F() object in place, each call to a QuerySet method (e.g. filter, exclude, order_by, distinct, etc.) takes approximately 2 seconds, but when I comment out the F() clause the calls are sub-second. I had a co-worker test it on his Ubuntu machine, and he is not experiencing the same performance issues I am with the F() clause.
Anyone else seeing this behavior?
class Move (models.Model):
state_meaning = models.CharField(
max_length=16,
db_index=True,
blank=True,
default=''
)
drop = models.ForeignKey(
Org,
db_index=True,
null=False,
default=1,
related_name='as_move_drop'
)
class Split(models.Model):
state_meaning = models.CharField(
max_length=16,
db_index=True,
blank=True,
default=''
)
move = models.ForeignKey(
Move,
related_name='splits'
)
pickup = models.ForeignKey(
Org,
db_index=True,
null=False,
default=1,
related_name='as_split_pickup'
)
pickup_date = models.DateField(
null=True,
default=None
)
drop = models.ForeignKey(
Org,
db_index=True,
null=False,
default=1,
related_name='as_split_drop'
)
drop_date = models.DateField(
null=True,
default=None,
db_index=True
)
def get_splits(begin_date, end_date):
qs = Split.objects \
.filter(state_meaning__in=['INPROGRESS','FULFILLED'],
drop=F('move__drop'), # <<< the line in question
pickup_date__lte=end_date)
elapsed = timer.clock() - start
print 'qs1 took %.3f' % elapsed
start = timer.clock()
qs = qs.filter(Q(drop_date__gte=begin_date) |
Q(drop_date__isnull=True))
elapsed = timer.clock() - start
print 'qs2 took %.3f' % elapsed
start = timer.clock()
qs = qs.exclude(move__state_meaning='UNFULFILLED')
elapsed = timer.clock() - start
print 'qs3 took %.3f' % elapsed
start = timer.clock()
qs = qs.order_by('pickup_date', 'drop_date')
elapsed = timer.clock() - start
print 'qs7 took %.3f' % elapsed
start = timer.clock()
qs = qs.distinct()
elapsed = timer.clock() - start
print 'qs8 took %.3f' % elapsed
