Write an Effective query for django for a FOR Loop?
I need to get number of policies bought in each month from these model
class Insurance(models.Model):
#other fields..
date_purchased_on = models.DateField(auto_now_add=True)
customer_region = models.CharField(
max_length=10, choices=RegionType.choices)
so i have written a views to get a response
@api_view(['GET'])
def chart_data(request):
# structure of the op should be all the months from 1 to 12
# [{"month": 1,"count": 100,}, { "month:2", "count":20}]
filtered_data = []
for i in range(1, 13):
query = Insurance.objects.filter(date_purchased_on__month=i).count()
data = {
"month": i,
"count": query
}
filtered_data.append(data)
return Response(filtered_data)
now the problem is this query hits the database every time its like 12 times. is there a way to handle this to get in a single query or to reduce it
and my logger results
(0.000) SELECT COUNT(*) AS "__count" FROM "insurance_insurance" WHERE EXTRACT('month' FROM "insurance_insurance"."date_purchased_on") = 1; args=(1,); alias=default
(0.000) SELECT COUNT(*) AS "__count" FROM "insurance_insurance" WHERE EXTRACT('month' FROM "insurance_insurance"."date_purchased_on") = 2; args=(2,); alias=default
(0.000) SELECT COUNT(*) AS "__count" FROM "insurance_insurance" WHERE EXTRACT('month' FROM "insurance_insurance"."date_purchased_on") = 3; args=(3,); alias=default
(0.000) SELECT COUNT(*) AS "__count" FROM "insurance_insurance" WHERE EXTRACT('month' FROM "insurance_insurance"."date_purchased_on") = 4; args=(4,); alias=default
(0.000) SELECT COUNT(*) AS "__count" FROM "insurance_insurance" WHERE EXTRACT('month' FROM "insurance_insurance"."date_purchased_on") = 5; args=(5,); alias=default
(0.000) SELECT COUNT(*) AS "__count" FROM "insurance_insurance" WHERE EXTRACT('month' FROM "insurance_insurance"."date_purchased_on") = 6; args=(6,); alias=default
(0.000) SELECT COUNT(*) AS "__count" FROM "insurance_insurance" WHERE EXTRACT('month' FROM "insurance_insurance"."date_purchased_on") = 7; args=(7,); alias=default
(0.000) SELECT COUNT(*) AS "__count" FROM "insurance_insurance" WHERE EXTRACT('month' FROM "insurance_insurance"."date_purchased_on") = 8; args=(8,); alias=default
(0.000) SELECT COUNT(*) AS "__count" FROM "insurance_insurance" WHERE EXTRACT('month' FROM "insurance_insurance"."date_purchased_on") = 9; args=(9,); alias=default
(0.000) SELECT COUNT(*) AS "__count" FROM "insurance_insurance" WHERE EXTRACT('month' FROM "insurance_insurance"."date_purchased_on") = 10; args=(10,); alias=default
(0.000) SELECT COUNT(*) AS "__count" FROM "insurance_insurance" WHERE EXTRACT('month' FROM "insurance_insurance"."date_purchased_on") = 11; args=(11,); alias=default
(0.000) SELECT COUNT(*) AS "__count" FROM "insurance_insurance" WHERE EXTRACT('month' FROM "insurance_insurance"."date_purchased_on") = 12; args=(12,); alias=default
You can extract the month and order by that month with an ExtractMonth
expression [Django-doc]:
from django.db.models import Count
from django.db.models.functions import ExtractMonth
Insurance.objects.values(month=ExtractMonth('date_purchased_on')).annotate(
count=Count('pk')
).order_by('month')
This will product a QuerySet
of dictionaries that look like:
<QuerySet [
{'month': 6, 'count': 100 },
{'month': 7, 'count': 20 }
]>
Months for which there is no Insurance
object will not be included in the QuerySet
. You thus might have to post-process it and include records with 'count': 0
for these.