Django - Access ForeignKey value without hitting database

Question

I have a django model like so:

class Profile_Tag(models.Model):
    profile = models.ForeignKey(Profile)
    tag = models.ForeignKey(Tag)

and a view like so:

pts = Profile_Tag.objects.all()
for pt in pts:
    print pt.profile.id

is there any way to access the profile foreignKey without hitting the database each time? I don't want to query the profile table. I just want to grab the ids from the Profile_Tag table.

Sexology

How do you know it "hits" the database? There is extensive cache management both in the ORM layer as well as the database. – Barclay

Well, to anyone else reading this and to answer Lott's question... it does do a DB hit in Django 1.4 (at least). You can turn on the database logging to see all the queries and pt.profile.id results in a query while pt.profile_id does not. It's possible for them to make the call to .id not result in a hit so it's possible this may change in the future (or already is different, I haven't tested newer versions). – Friede

Answer 1

You can do something like this:

pt_ids = Profile_Tag.objects.values_list('profile', flat=True)

This will return you list of IDs. For model instance, there's another way:

pts = Profile_Tag.objects.all()
for pt in pts:
    print pt.profile_id

Sidran

excellent. thank you. guess i should have thought to try that – Sexology