Django 2.1 ProgrammingError at /admin column + _id does not exist - django

Question

While trying to run my second Django 2.1 /Postgres 10 project I got stuck with the following programming error:
ProgrammingError at /admin/vocs_app/subsubscriber/
column sub_subscriber.sub_prev_sst_uid_id does not exist
LINE 1: ...", "sub_subscriber"."sub_next_recharge_datetime", "sub_subsc...
^
HINT: Perhaps you meant to reference the column "sub_subscriber.sub_prev_sst_uid".
I can open the admin app of my application, i.e., 127.0.0.1:8000/admin/vocs_app.
It lists all imported models from my database; to illustrate my case I believe the following classes are sufficient:
(taken from my_site/vocs_app/models.py:)
from django.db import models
class VneVirtualNetwork(models.Model):
vne_uid = models.BigAutoField(primary_key=True)
vne_nop_uid = models.ForeignKey(NopNetworkOperator, models.DO_NOTHING, db_column='vne_nop_uid')
vne_name = models.CharField(max_length=50)
vne_code = models.CharField(max_length=50)
vne_external_id = models.CharField(max_length=100, blank=True, null=True)
vne_idd_code = models.CharField(max_length=5)
vne_sn_length = models.IntegerField()
createdon = models.DateTimeField()
createdby = models.CharField(max_length=150)
createdfrom = models.CharField(max_length=150)
modifiedon = models.DateTimeField()
modifiedby = models.CharField(max_length=150)
modifiedfrom = models.CharField(max_length=150)
class Meta:
managed = False
db_table = 'vne_virtual_network'
class SstSystemStatus(models.Model):
sst_uid = models.BigAutoField(primary_key=True)
sst_name = models.CharField(max_length=50)
sst_description = models.CharField(max_length=100, blank=True, null=True)
startdate = models.DateField(blank=True, null=True)
enddate = models.DateField(blank=True, null=True)
class Meta:
managed = False
db_table = 'sst_system_status'
class SubSubscriber(models.Model):
sub_uid = models.BigAutoField(primary_key=True)
sub_vne_uid = models.ForeignKey('VneVirtualNetwork', models.DO_NOTHING, db_column='sub_vne_uid')
sub_rpl_uid = models.ForeignKey(RplRatePlan, models.DO_NOTHING, db_column='sub_rpl_uid')
sub_account_user_id = models.CharField(max_length=100, blank=True, null=True)
sub_external_id = models.CharField(max_length=100)
sub_hzn_uid = models.ForeignKey(HznHomezoneName, models.DO_NOTHING, db_column='sub_hzn_uid')
sub_low_balance_trigger = models.BooleanField()
sub_first_call_datetime = models.DateTimeField(blank=True, null=True)
sub_last_enabled_datetime = models.DateTimeField(blank=True, null=True)
sub_last_disabled_datetime = models.DateTimeField(blank=True, null=True)
sub_last_recharge_datetime = models.DateTimeField(blank=True, null=True)
sub_next_recharge_datetime = models.DateTimeField(blank=True, null=True)
sub_prev_sst_uid = models.ForeignKey(SstSystemStatus, related_name='sub_prev_sst_uid',on_delete=models.DO_NOTHING)
sub_sst_uid = models.ForeignKey(SstSystemStatus, related_name='sub_sst_uid',on_delete=models.DO_NOTHING)
startdatetime = models.DateTimeField()
enddatetime = models.DateTimeField()
createdon = models.DateTimeField()
createdby = models.CharField(max_length=150)
createdfrom = models.CharField(max_length=150)
modifiedon = models.DateTimeField()
modifiedby = models.CharField(max_length=150)
modifiedfrom = models.CharField(max_length=150)
class Meta:
managed = False
db_table = 'sub_subscriber'
class SubSubscriber references foreign key sst_uid of table/class SstSystemStatus twice (previous and current status). It seems Django doesn't like it. Other tables such as VneVirtualNetwork (which contain a "single" foreign key references) don't cause any issue. The admin GUI allows me to display and change their data.
The fault message shows that Django tries to complement the name of field sub_prev_sst_uid with '_id'. If I comment the relevant line in file model.py and try to display the subscriber table it will cause the same error, this time with field sub_sst_uid. How can I prevent Django from appending '_id'?
Thanks in advance for any advice.

Answer 1

By default, Django will use the related name and/or the chosen class field name, add a suffix "_id" and try to locate a column of this name in the database. Unless you explicitly define the db_column as follows:
sub_sst_uid = models.ForeignKey('SstSystemStatus', db_column='sub_sst_uid', related_name='sub_sst_uid', on_delete=models.DO_NOTHING)
sub_prev_sst_uid = models.ForeignKey('SstSystemStatus', db_column='sub_prev_sst_uid', related_name='sub_prev_sst_uid', on_delete=models.DO_NOTHING)