how do increment all column values in db table after certain integer values in that column (django)?

Question

Suppose I have created "X" database table in Django which has column id(autofiled), name(charfield) and occurrence(integerfield), now suppose 3 rows are already available in it

id	name	occurrence
1	ABC	1
2	BCD	2
3	CDE	3

I want to get data based on (ordering) the occurance number, I am facing a problem that, I want to add a row with an occurrence number 2 (already present), and all the rows with occurrence numbers greater than 2 update and increment automatically. (Basically, It is a inserting data on index number, where value is name and index is occurrence ignore id). For Example-

id	name	occurrence
1	ABC	1
2	BCD	3
3	CDE	4
4	XYZ	2

Thanks in advance.

Answer 1

class FooBar(models.Model):
    occurrence = models.IntegerField()
    name = models.CharField(max_length=100)

    def save(self, *args, **kwargs):
        same_occurrence = FooBar.objects.filter(occurrence=self.occurrence).first()
        if same_occurrence:
            same_occurrence.occurrence = self.occurrence + 1
            same_occurrence.save()
        return super(FooBar, self).save(*args, **kwargs)