Optimise Two Sql Queries And A List Comprehension

I have those two models (simplified): class Place(OrderedModel): name = models.CharField(max_length=100) class Team(models.Model): name = models.CharField(max_length=100)

Solution 1:

You need this SQL query:

SELECT P.id, (TP.id ISNOTNULL) AS done
FROM myapp_place P
LEFTOUTERJOIN myapp_team_places TP
ON P.id = TP.place_id AND TP.team_id =%s

(You'll also need to add an ORDER BY clause to return the Place objects in the order you want, but since I can't see that part of your model, I can't tell what that clause ought to look like.)

I don't know how to express this query using Django's object-relational mapping system, but you can always run it using a raw SQL query:

>>>sql = ''' ... as above ... '''>>>places = Place.objects.raw(sql, [team.id])>>>for p in places:...print p.id, bool(p.done)...
1 True
2 True
3 False

Solution 2:

A more optimal solution would be:

defdone(self):    
    places = Place.objects.values_list('pk', flat=True)
    team_places = self.places.values_list('pk', flat=True)

    return [place in team_places for place in places]