迁移 Django 模型时如何解决错误？

Question

I want to migrate my model for create tables on my local PgSQL DB. It's not the first time that I'm doing that on this configuration but this time, that's fail.

My manipulation :

1) I deleted my old database jlb_inventory

2) I recreated the database jlb_inventory empty

3) I deleted "0001_initial" on application's directory /migration

4) I ran command python manage.py makemigrations => Error

models.py

# Table Etude
class Study(models.Model):
    study_name = models.CharField(max_length=255, null=False)



class Inventory(models.Model):
    watercourse = models.CharField(max_length=255, null=False)
    town = models.CharField(max_length=255, null=False)
    number_resorts = models.IntegerField(null=False)
    inventory_date = models.DateField(null=False)
    fk_study = models.ForeignKey(Study, on_delete=models.CASCADE)



class Resort(models.Model):
    index_resort = models.IntegerField(null=False)
    name_resort = models.CharField(max_length=255)
    fk_inventory = models.ForeignKey(Inventory, on_delete=models.CASCADE)


class Taxon(models.Model):
    name_taxon = models.CharField(max_length=255, null=False)
    gi = models.IntegerField(default=0)


class Sample(models.Model):
    MICRO_HABITAT_CHOICES = (
        ('1', 'Habitat1'),
        ('2', 'Habitat2'),
        ('3', 'Habitat3'),
        ('4', 'Habitat4'),
        ('5', 'Habitat5'),
        ('6', 'Habitat6'),
        ('7', 'Habitat7'),
        ('8', 'Habitat8'),
    )

    taxon_quantity = models.IntegerField(null=False)
    fk_taxon = models.ForeignKey(Taxon, on_delete=models.CASCADE)
    fk_resort = models.ForeignKey(Resort, on_delete=models.CASCADE)

And my error

django.db.utils.ProgrammingError: relation "business_data_entry_taxon" does not exist
LINE 1: ...ame_taxon", "business_data_entry_taxon"."gi" FROM "business_...

Someone knows what is the problem here ? Thanks!

Answer 1

I tested your app and it is working(django 2.2). If you delete db and recreate new db so normally it is working but somehow I think you need first migration for your db.

So, remove app INSTALLED_APPS, and recreate db and remove all migrations. Then run makemigrations and migrate. Then add your app to INSTALLED_APPS, run again makemigrations and migrate.

Answer 2

I post an aswer but I don't have a structuration explication about the solution.

In my app, I've 4 forms and 2 call the DB for ChoiceField . I tried to comment all my path in urls.py and ran command makemigrations and migrate . That's work ...

I think, before execute the command, Django "compile" (or something like that) my code and try to set ChoiceField but he can't find something because I deleted the DB before.

I encourage someone to comment this post for more explications then, i'll edit this aswer.