django.db.utils.IntegrityError: duplicate key value violates unique constraint - django

Question

I have Country model
from django.db import models
class Country(models.Model):
country = models.CharField(max_length = 20, primary_key=True)
country_id = models.IntegerField()
I uploaded some data in Country table with following custom management command
from django.core.management.base import BaseCommand, CommandError
from data.models import Country
import json
from .extract_country import extracting
get_parsed_json = extracting()
def store_data():
for key, value in get_parsed_json['api']['countries'].items():
country_id_field = key
country_name = value
One_country = Country.objects.create(country_id = country_id_field , country = country_name)
One_country.save()
print(One_country)
class Command(BaseCommand):
def handle(self, **options):
extracting()
store_data()
Now i am trying to upload to the Country table extended data which contain the same countries and another but when i am trying to upload data i get the following error. Here is my full traceback
Traceback (most recent call last):
File "D:\Python\my_projects\forecast\lib\site-packages\django\db\backends\util
s.py", line 85, in _execute
return self.cursor.execute(sql, params)
psycopg2.IntegrityError: duplicate key value violates unique constraint "data_co
untry_name_04df4fc7_uniq"
DETAIL: Key (country)=(Algeria) already exists.
The above exception was the direct cause of the following exception:
Traceback (most recent call last):
File "manage.py", line 15, in <module>
execute_from_command_line(sys.argv)
File "D:\Python\my_projects\forecast\lib\site-packages\django\core\management\
__init__.py", line 381, in execute_from_command_line
utility.execute()
File "D:\Python\my_projects\forecast\lib\site-packages\django\core\management\
__init__.py", line 375, in execute
self.fetch_command(subcommand).run_from_argv(self.argv)
File "D:\Python\my_projects\forecast\lib\site-packages\django\core\management\
base.py", line 316, in run_from_argv
self.execute(*args, **cmd_options)
File "D:\Python\my_projects\forecast\lib\site-packages\django\core\management\
base.py", line 353, in execute
output = self.handle(*args, **options)
File "D:\Python\my_projects\forecast\project\forecasting\data\management\comma
nds\upload_country.py", line 23, in handle
store_data()
File "D:\Python\my_projects\forecast\project\forecasting\data\management\comma
nds\upload_country.py", line 14, in store_data
One_country = Country.objects.create(country_id = country_id_field , country
= country_name)
File "D:\Python\my_projects\forecast\lib\site-packages\django\db\models\manage
r.py", line 82, in manager_method
return getattr(self.get_queryset(), name)(*args, **kwargs)
File "D:\Python\my_projects\forecast\lib\site-packages\django\db\models\query.
py", line 413, in create
obj.save(force_insert=True, using=self.db)
File "D:\Python\my_projects\forecast\lib\site-packages\django\db\models\base.p
y", line 718, in save
force_update=force_update, update_fields=update_fields)
File "D:\Python\my_projects\forecast\lib\site-packages\django\db\models\base.p
y", line 748, in save_base
updated = self._save_table(raw, cls, force_insert, force_update, using, upda
te_fields)
File "D:\Python\my_projects\forecast\lib\site-packages\django\db\models\base.p
y", line 831, in _save_table
result = self._do_insert(cls._base_manager, using, fields, update_pk, raw)
File "D:\Python\my_projects\forecast\lib\site-packages\django\db\models\base.p
y", line 869, in _do_insert
using=using, raw=raw)
File "D:\Python\my_projects\forecast\lib\site-packages\django\db\models\manage
r.py", line 82, in manager_method
return getattr(self.get_queryset(), name)(*args, **kwargs)
File "D:\Python\my_projects\forecast\lib\site-packages\django\db\models\query.
py", line 1136, in _insert
return query.get_compiler(using=using).execute_sql(return_id)
File "D:\Python\my_projects\forecast\lib\site-packages\django\db\models\sql\co
mpiler.py", line 1289, in execute_sql
cursor.execute(sql, params)
File "D:\Python\my_projects\forecast\lib\site-packages\django\db\backends\util
s.py", line 100, in execute
return super().execute(sql, params)
File "D:\Python\my_projects\forecast\lib\site-packages\django\db\backends\util
s.py", line 68, in execute
return self._execute_with_wrappers(sql, params, many=False, executor=self._e
xecute)
File "D:\Python\my_projects\forecast\lib\site-packages\django\db\backends\util
s.py", line 77, in _execute_with_wrappers
return executor(sql, params, many, context)
File "D:\Python\my_projects\forecast\lib\site-packages\django\db\backends\util
s.py", line 85, in _execute
return self.cursor.execute(sql, params)
File "D:\Python\my_projects\forecast\lib\site-packages\django\db\utils.py", li
ne 89, in __exit__
raise dj_exc_value.with_traceback(traceback) from exc_value
File "D:\Python\my_projects\forecast\lib\site-packages\django\db\backends\util
s.py", line 85, in _execute
return self.cursor.execute(sql, params)
django.db.utils.IntegrityError: duplicate key value violates unique constraint "
data_country_name_04df4fc7_uniq"
DETAIL: Key (country)=(Algeria) already exists.
I found that is very frequent problem for django users but didnt find how to fix it. Any suggestions ?

Answer 1

Seems that you try to create County with same county name as it's your primary key.
Try to use get_or_create():
def store_data():
for key, value in get_parsed_json['api']['countries'].items():
country_id_field = key
country_name = value
one_country, created = Country.objects.update_or_create(
country_id=country_id_field
defaults={'country': country_name},
)
# one_country.save() <- no need to save after create or get_or_create method.
print(one_country)

Answer 2

The primary key must be unique, if there is an instance with the key "Algeria" already exists, you cannot create a second instance with the same key.
Instead of:
One_country = Country.objects.create(country_id = country_id_field , country = country_name)
You could use get_or_create:
# ...
One_country, created = Country.objects.get_or_create(country=country_name)
One_country.country_id = country_id_field
One_country.save()
# ...