Django - improve the query consisting many-to-many and foreignKey fields

Question

I want to export a report from the available data into a CSV file. I wrote the following code and it works fine. What do you suggest to improve the query?

Models:

class shareholder(models.Model):
   title = models.CharField(max_length=100)
   code = models.IntegerField(null=False)

class Company(models.Model):
   isin = models.CharField(max_length=20, null=False)
   cisin = models.CharField(max_length=20)
   name_fa = models.CharField(max_length=100)
   name_en = models.CharField(max_length=100)

class company_shareholder(models.Model):
   company = models.ManyToManyField(Company)
   shareholder = models.ForeignKey(shareholder, on_delete=models.SET_NULL, null=True)
   share = models.IntegerField(null = True) # TODO: *1000000 
   percentage = models.DecimalField(max_digits=8, decimal_places=2, null=True)
   difference = models.DecimalField(max_digits=11, decimal_places=2, null=True)
   update_datetime = models.DateTimeField(null=True)

View:

def ExportAllShare(request):
   response = HttpResponse(content_type='text/csv')
   response['Content-Disposition'] = 'attachment; filename="shares.csv"'
   response.write(u'\ufeff'.encode('utf8'))
   writer = csv.writer(response)
   writer.writerow(['date','company','shareholder title','shareholder code','difference','share'])
   results = company_shareholder.objects.all()
   for result in results:
      row = (
        result.update_datetime,
        result.company.first().name_fa,
        result.shareholder.title,
        result.shareholder.code,
        result.difference,
        result.share,
           )
      writer.writerow(row)
   return (response)

Answer 1

First of all if it's working fine for you, then it's working fine, don't optimize prematurely.

But, in a query like this you are running into n+1 problem. In Django you avoid it using select_related and prefetch_related. Like this:

results = company_shareholder.objects.select_related('shareholder').prefetch_related('company').all()

This should reduce the number of queries you are generating. If you need a little bit more performance and since you are not using percentage I would defer it.

Also, I would highly suggest you follow PEP8 styling guide and name your classes in CapWords convention like Shareholder and CompanyShareholder.