I'm trying to look at the most efficient way to traverse my models to get the data that I'm after. I have three "related" models. Item, ProtectionList and Player
Protection List
class ProtectionList(models.Model):
player = models.ForeignKey(Player)
main_hand = models.ForeignKey(Item, null=True, blank=True, related_name='main_hand')
off_hand = models.ForeignKey(Item, null=True, blank=True, related_name='off_hand')
head = models.ForeignKey(Item, null=True, blank=True, related_name='head')
neck = models.ForeignKey(Item, null=True, blank=True, related_name='neck')
shoulder = models.ForeignKey(Item, null=True, blank=True, related_name='shoulder')
back = models.ForeignKey(Item, null=True, blank=True, related_name='back')
chest = models.ForeignKey(Item, null=True, blank=True, related_name='chest')
wrist = models.ForeignKey(Item, null=True, blank=True, related_name='wrist')
hands = models.ForeignKey(Item, null=True, blank=True, related_name='hands')
waist = models.ForeignKey(Item, null=True, blank=True, related_name='waist')
legs = models.ForeignKey(Item, null=True, blank=True, related_name='legs')
feet = models.ForeignKey(Item, null=True, blank=True, related_name='feet')
ring1 = models.ForeignKey(Item, null=True, blank=True, related_name='ring1')
ring2 = models.ForeignKey(Item, null=True, blank=True, related_name='ring2')
trinket1 = models.ForeignKey(Item, null=True, blank=True, related_name='trinket1')
trinket2 = models.ForeignKey(Item, null=True, blank=True, related_name='trinket2')
locked = models.BooleanField(default=False)
def __unicode__(self):
return self.player.main_character.name
Player
class Player(models.Model):
accountID = models.CharField(max_length=255, null=True, blank=True)
battletag = models.CharField(max_length=255, null=True, blank=True)
user = models.OneToOneField(User, null=True, blank=True)
main_character = models.ForeignKey('Character', null=True, blank=True, related_name='main_character')
signature = models.TextField(null=True, blank=True)
def __unicode__(self):
return self.battletag
Item
class Item(models.Model):
'''Details individual data for each item on a loot table'''
name = models.CharField(max_length=255, null=True)
item_id = models.IntegerField(null=True)
dropped_by = models.ForeignKey(Boss)
warforgeable = models.BooleanField(default=True)
bonus_string = models.CharField(max_length=255, blank=True, null=True)
def __unicode__(self):
return self.name
I need to map my way back to the Player to make a list of Player objects dependant on who has the Item in any field on their ProtectedList.
I know Item is related to ProtectionList and ProtectionList to Player however I want to find an efficient way of checking in all the fields where Item is a ForeignKey within the ProtectionList object as the Item being filtered could potentially be in any field (minus the player and locked fields).
I have considered the use of Q to OR each of the fields, but I'm not sure how optimal this would be on larger querysets.
I am also looking at through intermediate tables and changing the model to a many-to-many.
I may be wrong, but i feel like your model structure is not normalized. You have a M2M relation between Player and Item via Slots. Consider the following model structure:
from django.db import models
from django.contrib.auth.models import User
class Slot(models.Model):
#e.g. main_hand, off_hand, head, ... , feet
name = models.CharField(max_length=255)
def __unicode__(self):
return self.name
class Item(models.Model):
'''Details individual data for each item on a loot table'''
name = models.CharField(max_length=255, null=True)
item_id = models.IntegerField(null=True)
"""removed for the example"""
#dropped_by = models.ForeignKey(Boss)
warforgeable = models.BooleanField(default=True)
bonus_string = models.CharField(max_length=255, blank=True, null=False, default='')
def __unicode__(self):
return self.name
class PlayerManager(models.Manager):
def create_player_with_empty_slots(self, **kwargs):
player = Player.objects.create(**kwargs)
PlayerSlot.objects.bulk_create([
PlayerSlot(player=player, slot=slot) for slot in Slot.objects.all()
])
return player
class Player(models.Model):
user = models.OneToOneField(User, null=True, blank=True)
"""removed for the example"""
#accountID = models.CharField(max_length=255, null=True, blank=True)
#battletag = models.CharField(max_length=255, null=True, blank=True)
#main_character = models.ForeignKey('Character', null=True, blank=True, related_name='main_character')
#signature = models.TextField(null=True, blank=True)
slots = models.ManyToManyField(Slot, through='PlayerSlot')
items = models.ManyToManyField(Item, through='PlayerSlot')
objects = PlayerManager()
def __unicode__(self):
"""changed for the example"""
return self.user.username
def get_slot(self, slot_or_slotname):
if isinstance(slot_or_slotname, Slot):
return self.playerslot_set.get(slot=slot_or_slotname)
else:
return self.playerslot_set.get(slot__name=slot_or_slotname)
def set_item(self, item, at_slot):
slot = self.get_slot(at_slot)
slot.item = item
slot.save()
class PlayerSlot(models.Model):
player = models.ForeignKey(Player)
slot = models.ForeignKey(Slot)
#item is optional, to allow empty slots
item = models.ForeignKey(Item, null=True, blank=True)
locked = models.BooleanField(default=False)
class Meta:
unique_together = ('player', 'slot')
def __unicode__(self):
return "{player} carry {item} on {slot}".format(player=self.player, item=self.item or 'nothing', slot=self.slot)
>>> from django.contrib.auth.models import User
>>> from game.models import Slot, Item, Player, PlayerSlot
Lets create some initial data:
>>> Slot.objects.bulk_create([
... Slot(name='main_hand'),
... Slot(name='off_hand'),
... Slot(name='head'),
... Slot(name='neck'),
... Slot(name='shoulder'),
... Slot(name='back'),
... Slot(name='chest'),
... Slot(name='wrist'),
... Slot(name='hands'),
... Slot(name='waist'),
... Slot(name='legs'),
... Slot(name='feet'),
... Slot(name='ring1'),
... Slot(name='ring2'),
... Slot(name='trinket1'),
... Slot(name='trinket2'),
... ])
[<Slot: main_hand>, <Slot: off_hand>, <Slot: head>, <Slot: neck>, <Slot: shoulder>, <Slot: back>, <Slot: chest>, <Slot: wrist>, <Slot: hands>, <Slot: waist>, <Slot: legs>, <Slot: feet>, <Slot: ring1>, <Slot: ring2>, <Slot: trinket1>, <Slot: trinket2>]
>>> Item.objects.bulk_create([
... Item(name='Short Sword'),
... Item(name='Sabre'),
... Item(name='Broadsword'),
... Item(name='Apprentice Broadsword'),
... Item(name='Monster Hunter'),
... ])
[<Item: Short Sword>, <Item: Sabre>, <Item: Broadsword>, <Item: Apprentice Broadsword>, <Item: Monster Hunter>]
>>> user1 = User.objects.create_user('john', 'lennon@thebeatles.com', 'johnpassword')
>>> user2 = User.objects.create_user('paul', 'mccartney@thebeatles.com', 'mccartnypassword')
>>> player1 = Player.objects.create_player_with_empty_slots(user=user1)
>>> player2 = Player.objects.create_player_with_empty_slots(user=user2)
Get all player slots:
>>> player1.slots.all()
[<Slot: main_hand>, <Slot: off_hand>, <Slot: head>, <Slot: neck>, <Slot: shoulder>, <Slot: back>, <Slot: chest>, <Slot: wrist>, <Slot: hands>, <Slot: waist>, <Slot: legs>, <Slot: feet>, <Slot: ring1>, <Slot: ring2>, <Slot: trinket1>, <Slot: trinket2>]
Get all player items:
>>> player1.items.all()
[]
Adding new item?
>>> broadsword = Item.objects.get(name='Broadsword')
>>> player1.set_item(broadsword, at_slot='main_hand')
>>> player1.items.all()
[<Item: Broadsword>]
Check what is inside some slot?
>>> player1.get_slot('main_hand')
<PlayerSlot: john carry Broadsword on main_hand>
Find players having a item:
>>> Player.objects.filter(items=broadsword)
[<Player: john>]
Some more example's by Two-Bit Alchemist:
Here are some example queries for this model structure:
You have a Player object player and need to know what is in his/her left hand:
player.items.filter(slot__name='off_hand')[0].item # Could be None
You have an Item object item and wish to know what slot player has it equipped in:
PlayerSlot.objects.filter(player=player).filter(item=item)[0].slot.name
You have an Item object item and wish to know what players have this item at all:
PlayerSlot.objects.filter(item=item).all()
or
Player.objects.filter(slots__item=item).all()
depending on which object you'd rather work with. I haven't tested any of the queries above but this should get you started. Also note that chaining this way (queries 1 & 2) may throw IndexError if the relationships don't line up the way you think (e.g., player does not actually have item), so be prepared to possibly catch that.
I believe something like this can do the job:
plist_slots = [
'main_hand', 'off_hand', 'head', 'neck', 'shoulder',
'back', 'chest', 'wrist', 'hands', 'waist', 'legs',
'feet', 'ring1', 'ring2', 'trinket1', 'trinket2'
]
Slot.objects.bulk_create([
Slot(name=slot) for slot in plist_slots
])
plist = ProtectionList.objects.all().select_related(
*list(['player'] + plist_slots)
)
for p in plist:
PlayerSlot.objects.bulk_create([
PlayerSlot(
player=p.player,
item=getattr(p, slot),
slot=Slot.objects.get(name=slot)
) for slot in plist_slots
])