Django: Build up portfolio valuation table with two queryset - django-views

Question

I want build a portfolio position table based on those models (models.py):
class Portfolio(models.Model):
"""
Portfolio model, portfolio description
"""
id = models.UUIDField(primary_key=True,default=uuid.uuid4,editable=False)
code = models.CharField(max_length=100, blank=True)
class PortfolioPosition(models.Model):
"""
PortfolioPosition Model, instruments hold in portfolio
"""
portfolio = models.ForeignKey(Portfolio, on_delete=models.CASCADE, related_name='portfolio',null=True)
private_debt_issue = models.OneToOneField(PrivateDebtIssue, on_delete=models.CASCADE)
start_date = models.DateField(null=False, default=date.today)
end_date = models.DateField(null=True, blank=True)
quantity = models.DecimalField(max_digits=12, decimal_places=4, default=Decimal('1.0000'))
class PrivateDebtIssue(models.Model):
"""
Model representing a Private Debt instrument.
"""
id = models.UUIDField(primary_key=True,default=uuid.uuid4,editable=False)
name = models.CharField(max_length=250, blank=True)
class PrivateDebtIssueValuation(models.Model):
"""
DataPoint value
"""
private_debt_issue = models.ForeignKey(PrivateDebtIssue,on_delete=models.CASCADE, related_name='private_debt_issue')
date = models.DateField()
fund_value = models.DecimalField(max_digits=12, decimal_places=2, default=Decimal('0.00'))
Maybe is not the best way to handle it, but I want build a portfolio position table with all open private debt positions and the last value, based on a input date.
I wrote this code:
class PortfolioDetailView(DetailView):
model = Portfolio
context_object_name = 'portfolio'
template_name = 'private_debts/portfolio_detail.html'
def get_context_data(self, **kwargs):
context = super().get_context_data(**kwargs)
# INPUT DATE BASED ON DATEPICKER
# set default date value
input_date = date.today()
if self.request.method == 'GET':
valuation_date = self.request.GET.get('valuation_date')
if valuation_date is not None:
input_date = datetime.strptime(valuation_date,'%m/%d/%Y')
# based on Portfolio object get portfolio positions and related PrivateDebtIssue objects
context['portfolio_position'] = PortfolioPosition.objects.all().select_related('portfolio','private_debt_issue').filter(
Q(portfolio=self.object)
& Q(start_date__lte=input_date)
& (Q(end_date__isnull=True) | Q(end_date__gte=input_date))
)
context['position_value'] = queryset
return context
This code works fine, but how do I get the value of the PrivateDebtIssue for a specific date and put it in a table?
I want to build a table with portfolio PortfolioPosition .position, PrivateDebtIssue.Name and PrivateDebtIssueValuation.fund_value, based on a valuation date.

Answer 1

At the end, I did something not recommended in Django: direct query with execute function. Like this
class PortfolioDetailView(DetailView):
model = Portfolio
context_object_name = 'portfolio'
template_name = 'private_debts/portfolio_detail.html'
def get_context_data(self, **kwargs):
context = super().get_context_data(**kwargs)
# set default date value
input_date = date.today()
input_date = date(2019,12,31)
if self.request.method == 'GET':
valuation_date = self.request.GET.get('valuation_date')
if valuation_date is not None:
input_date = datetime.strptime(valuation_date,'%m/%d/%Y')
sql = """
SELECT * \
FROM private_debts_portfolioposition \
INNER JOIN private_debts_privatedebtissue \
ON (private_debts_portfolioposition.private_debt_issue_id = private_debts_privatedebtissue.id) \
INNER JOIN private_debts_privatedebtissuevaluation \
ON (private_debts_privatedebtissuevaluation.private_debt_issue_id = private_debts_privatedebtissue.id) \
WHERE private_debts_portfolioposition.portfolio_id = '{}'::uuid \
AND private_debts_privatedebtissuevaluation.date = '{}'
""".format(self.object.id, input_date)
portfolio_position = my_custom_sql(sql)
context['portfolio_position_table'] = portfolio_position
context['valuation_date'] = valuation_date
return context
And I used the example 'suggested' by the docs
These are the two functions:
def dictfetchall(cursor):
"Return all rows from a cursor as a dict"
columns = [col[0] for col in cursor.description]
return [
dict(zip(columns, row))
for row in cursor.fetchall()
]
def my_custom_sql(sql):
with connection.cursor() as cursor:
cursor.execute(sql)
row = dictfetchall(cursor)
return row
I hope someone could suggest a better way to handle it.
Thanks.