Reputation: 11363
Given the following models and an array of strings via a URI GET, how can I efficiently execute a filter operation and return all Trail
matches?
class Trail(models.Model):
'''
Main model for this application. Contains all information for a particular trail
'''
trail_name = models.CharField(max_length=150)
active = models.BooleanField(default=True)
date_uploaded = models.DateTimeField(default=now())
owner = models.ForeignKey(Account, default=1)
class Surface(models.Model):
'''
A many to many join table to map a surface type to many trails. A trail can have many
surface types.
'''
type = models.CharField(max_length=50, db_column='surface_type', unique=True)
trails = models.ManyToManyField(Trail)
class Meta:
ordering = ('type', )
Naively, I can just get all Trail models and iterate through them to get the matches, but would like a more efficient way.
I've attempted to do this:
from django.models.db import Q
#List of strings as a result of a URL querystring like
#?keys=Dirt&keys=Gravel&keys=Paved
keys = request.GET.getlist('keys')
queries = [Q(type = surface) for surface in keys]
query = queries.pop()
for item in queries:
query |= item
results = Trail.objects.filter(surface=type)
but this returns an ValueError: invalid literal for int() with base 10:
exception.
Upvotes: 0
Views: 884
Reputation: 600041
There's no need to use Q
here at all. What you presumably have is a list of strings corresponding to the type
field of Surface objects, and you want to get the Trails that are related to those Surfaces. You can use __in
to query for multiple surface types, and you can also use the double-underscore relationship to cross the relationship between Surface and Trail. So:
Trail.objects.filter(surface__type__in=request.GET.getlist('keys'))
Upvotes: 2