[FIXED] How should I generate cache keys

Issue

I want to cache following models and a shortened link for each Question.

class Question(models.Model):
    question_text = models.CharField('text', max_length=200)
    pub_date = models.DateTimeField('publication date', default=timezone.now)
    allow_multiple_choices = models.BooleanField(default=False)


class Choice(models.Model):
    question = models.ForeignKey(Question, on_delete=models.CASCADE)
    choice_text = models.CharField('text', max_length=200)
    votes = models.IntegerField('votes', default=0)

    def __str__(self):
        return self.choice_text

How should I generate keys? Is something like this sufficient?

cache.set('question' + question.id, question)
cache.set('shortened' + question.id, shortened)

Solution

This should do. But am not sure about the scope of the instances created. If they are global, we have guaranteed non-overlapping of keys.

From the documentation of id

Return the “identity” of an object. This is an integer (or long integer) which is guaranteed to be unique and constant for this object during its lifetime. Two objects with non-overlapping lifetimes may have the same id() value.

May be you should try other approaches, which guarantees keys uniqueness for your collection and also have a uniform distribution. In our implementation, we will generate some hashcode (md5 or sha1) from instance identification data.

Answered By - arunk2

Answer Checked By - Dawn Plyler (PHPFixing Volunteer)