Importing simple table to Django seems to generate extraneous field

Using Django
1

This is my table as defined in MySQL:

mysql> describe rules_enabled;
+-------------------+----------------------------------+------+-----+---------+----------------+
| Field             | Type                             | Null | Key | Default | Extra          |
+-------------------+----------------------------------+------+-----+---------+----------------+
| rule_id           | int                              | NO   | PRI | NULL    | auto_increment |
| rule_name         | varchar(20)                      | NO   | MUL | NULL    |                |
| role_name         | varchar(20)                      | NO   | MUL | NULL    |                |
| role_dependency   | varchar(20)                      | YES  | MUL | NULL    |                |
| range_application | enum('PERIOD','WIDE','REF_DATE') | NO   |     | PERIOD  |                |
| range_duration    | int                              | YES  |     | -1      |                |
| reference_date    | timestamp                        | YES  |     | NULL    |                |
| rule_parameters   | json                             | YES  |     | NULL    |                |
+-------------------+----------------------------------+------+-----+---------+----------------+

and this is how it is understood by Django doing manage.py inspectdb rules_enabled:

class RulesEnabled(models.Model):
    rule_id = models.AutoField(unique=True)
    rule_name = models.CharField(max_length=20, db_comment='Rule name')
    role_name = models.ForeignKey('ShiftRoles', models.DO_NOTHING, db_column='role_name')
    role_dependency = models.ForeignKey('ShiftRoles', models.DO_NOTHING, db_column='role_dependency', related_name='rulesenabled_role_dependency_set', blank=True, null=True)
    range_application = models.CharField(max_length=8, db_comment='Type of range used to evaluae the rule.')
    range_duration = models.IntegerField(blank=True, null=True, db_comment='Extension of the range (WIDE Only) in days.')
    reference_date = models.DateTimeField(blank=True, null=True, db_comment='Reference day (REF_DATE ONLY).')
    rule_parameters = models.JSONField(blank=True, null=True, db_comment='Rule parameters')

    class Meta:
        managed = False
        db_table = 'rules_enabled'
        db_table_comment = 'Rules associated to the defined roles'

problem 1, using it like this in file models.py, running manage.py makemigrations gives:

  File "/usr/local/django_venv/lib/python3.10/site-packages/django/db/models/fields/__init__.py", line 2812, in contribute_to_class 
raise ValueError(
ValueError: Model b2mmsdb.RulesEnabled can't have more than one auto-generated field.

(I think this is because of the Django-created extra id, it doesn’t like the name of my own PK) Next, I change line

    rule_id = models.AutoField(unique=True)

to

    rule_id = models.AutoField(primary_key=True)

Django does allright makemigrations and migrate but now, in the Django shell, I get:

>>> rule_205=RulesEnabled.objects.filter(rule_id=205).get()
>>> print(rule_205.rule_name)
overlap                        <--------------fantastic! it's even right!
>>> RulesEnabled.objects.filter(rule_name='overlap').count()
23                             <------still OK. But, waitaminute.....

>>> print(rule_205.role_name)
Traceback (most recent call last):
  File "/usr/local/django_venv/lib/python3.10/site-packages/django/db/models/fields/related_descriptors.py", line 236, in __get__
    rel_obj = self.field.get_cached_value(instance)
  File "/usr/local/django_venv/lib/python3.10/site-packages/django/db/models/fields/mixins.py", line 15, in get_cached_value
    return instance._state.fields_cache[cache_name]
KeyError: 'role_name'          <---------------- huh?
(....more traceback from Django innards...)
ValueError: Field 'role_id' expected a number but got 'cr_shadow_loc'.

>>> RulesEnabled.objects.filter(role_name='cr_shadow_loc').count()
Traceback (most recent call last):
  File "/usr/local/django_venv/lib/python3.10/site-packages/django/db/models/fields/__init__.py", line 2117, in get_prep_value
    return int(value)
ValueError: invalid literal for int() with base 10: 'cr_shadow_loc'
....
ValueError: Field 'role_id' expected a number but got 'cr_shadow_loc'.

Now, where does role_id come from, and why Django seems to believe is a PK? Let’s have a look at all fields:

>>> field_names = [f.name for f in RulesEnabled._meta.get_fields()]
>>> print(field_names)
['rule_id', 'rule_name', 'role_name', 'role_dependency', 'range_application', 'range_duration', 'reference_date', 'rule_parameters']

No role_id that I can see. This is not the first table I import to Django, have seen and fixed other strange facts, but can’t figure out this at all.

Please help, or suggest other debugging shell commands. Thank you!!

2

Well, it happens that role_id is in another table, and it comes into play because role_name in my malfunctioning table is a FK relation to that. So, I have to add a clause to_field, changing line:

role_name = models.ForeignKey('ShiftRoles', models.DO_NOTHING, db_column='role_name')

to

role_name = models.ForeignKey('ShiftRoles', models.DO_NOTHING, db_column='role_name',to_field='role_name')

As simple as that. Thanks for reading!