Hello,
I'm trying to use select_related() with a OneToOneField. But I'm
worried about the number of queries it executes. From the django
documentation: select_related(): "[...] selecting that additional
related-object data when it executes its query [...]". So when I append
select_related() to a object, it should make one query to my database
only, at least that's how I understand it.
I'm using the following model:
-------------------- models.py -------------------------
class Player(models.Model):
name = models.CharField(maxlength=100, unique=True)
nation = models.CharField(choices=NATION_CHOICES, maxlength=20,
radio_admin=True)
pub_date = models.DateTimeField(auto_now_add=True)
def __str__(self):
return self.name
class Admin:
pass
class License(models.Model):
player = models.OneToOneField(Player)
vid = models.IntegerField(blank=True, null=True)
combat = models.IntegerField(blank=True,null=True)
light = models.IntegerField(blank=True,null=True)
heavy = models.IntegerField(blank=True,null=True)
trade = models.IntegerField(blank=True,null=True)
mining = models.IntegerField(blank=True,null=True)
kplayers = models.IntegerField(blank=True,null=True)
kbots = models.IntegerField(blank=True,null=True)
deaths = models.IntegerField(blank=True,null=True)
misingle = models.IntegerField(blank=True,null=True)
migroup = models.IntegerField(blank=True,null=True)
pub_date = models.DateTimeField(auto_now_add=True)
def __str__(self):
return "%s/%s/%s/%s/%s" % (self.combat, self.light,
self.heavy, self.trade, self.mining)
class Admin:
pass
---------------------------------------
Now I want to query the data from the Player and License model like
this:
>>> from django.db import connection
>>> from clmdb.data.models import *
>>> len(connection.queries)
0
>>> p = Player.objects.select_related()
>>> x = "%s %s %s %s %s" % (p[0].license.combat, p[0].license.light,
>>> p[0].license.heavy, p[0].license.trade, p[0].license.mining)
>>> print x
3 6 4 7 9
>>> len(connection.queries)
10
So selecting the License model through the OneToOne key creates 10
queries. As you can imagine this adds up to 600 in larger tables... So
I guess I'm not using select_related() correctly and I hope somebody
can tell me how to use it so that it only makes one query. All I
basically need is a JOIN.
Thanks for your time.
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