What is a standard practice to drop tables of an app in Django?

[Jae Pil Choi]

I'm asking this on the official Django community after I asked on Stackoverflow because I still don't know what is the best practice for this particular action. 

(Original Question on Stackoverflow here: What is Django commend equivalent to Rails' $ rails db drop)

My scenario goes as follow: 

1. I create 2 model class objects, Post, Product in models.py 

2. Post has 2 attributes: post_title, post_text. Product has its own but that's irrelevant. 

3. I make migrations and migrate. 

4. Then I go to /admin of my page and add some rows both on Post and Product. 

5. Now I remember that I I forgot to add an attribute post_author on Post and adds it in models.py

6. If I make migrations, Django warns me that already existing rows needs default values since they don't have this new attributes. 

7. I don't want any post without an author so I want to drop this existing rows and make it all again. 

8. However, I don't want to lose any Product rows already created. 

Here's the question: How do I drop ONLY Post table leaving Product and my Superuser intact? 

Original Stackoverflow post suggests manually removing db.sqlite3 file and migrations files but I really don't think this is the way to go and there must be some best practice or commend for this since Django is already at 2.1.

If not, I think there must be a good reason not to have one and I want to know why. 

[Mike Dewhirst]

On 8/09/2018 9:09 PM, Jae Pil Choi wrote:
> I'm asking this on the official Django community after I asked on
> Stackoverflow because I still don't know what is the best practice for
> this particular action.
>
> (Original Question on Stackoverflowhere

> <https://stackoverflow.com/questions/52225453/what-is-django-commend-equivalent-to-rails-rails-db-drop/52226394?noredirect=1#comment91407548_52226394>:

> What is Django commend equivalent to Rails' $ rails db drop)
>
> My scenario goes as follow:
>
> 1. I create 2 model class objects, Post, Product in models.py
> 2. Post has 2 attributes: post_title, post_text. Product has its own
> but that's irrelevant.
> 3. I make migrations and migrate.
> 4. Then I go to /admin of my page and add some rows both on Post and
> Product.
>
> 5. Now I remember that I I forgot to add an attribute post_author on
> Post and adds it in models.py
> 6. If I make migrations, Django warns me that already existing rows
> needs default values since they don't have this new attributes.
> 7. I don't want any post without an author so I want to drop this
> existing rows and make it all again.
> 8. However, I don't want to lose any Product rows already created.
>
>
> Here's the question: How do I drop ONLY Post table leaving Product and
> my Superuser intact?

You need a custom migration ... ./migrations/remove_authorless_rows.py

def forwards_func(apps, schema_editor):
    Model_class = apps.get_model("<app name>", "Model_class")
    db_alias = schema_editor.connection.alias
    Model_class.objects.using(db_alias).filter(author=None).delete()

class Migration(migrations.Migration):

    dependencies = [
        ('<app name>', '<most recent previous successful migration>'),
    ]

    operations = [
        migrations.RunPython(
            forwards_func,
        ),
    ]

This is off the top of my head so you would need to test it in a sandbox
and repair as required.

>
> Original Stackoverflow post suggests manually removing db.sqlite3 file
> and migrations files but I really don't think this is the way to go
> and there must be some best practice or commend for this since Django
> is already at 2.1.
>
> If not, I think there must be a good reason not to have one and I want
> to know why.
>
>
>

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[mottaz hejaze]

make the attribute post_auther null = True , then make migrations

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