Applied migration detection may fail when using a case-insensitive collation

[Elaci0]

Hello,
I'm using this guide ​https://datascience.blog.wzb.eu/2017/03/21/using-django-with-an-existinglegacy-database for my studies with camelCasing together with Django (yes, I'm still trying to keep the naming convention we have inside our DB, also for the model's names)

Now, I'm really new to Django and I don't know if it's intended but this part of code inside django/db/migrations/executor.py' is doing case sensitive comparison to check if a column is already present in a database

column_names = [
    column.name for column in
    self.connection.introspection.get_table_description(self.connection.cursor(), table)
]
if field.column not in column_names:
    return False, project_state

so if my migration file contains something like this

        migrations.AddField(
            model_name='city',
            name='countrycode',
            field=models.ForeignKey(db_column='countryCode', on_delete=django.db.models.deletion.CASCADE, to='my_DB.country'),

and I run python3 manage.py migrate --database my_DB --fake-initial my_first_app

it fires an error saying that that table already exists
django.db.utils.OperationalError: (1050, "Table 'city' already exists")

If I run python3 manage.py migrate --database my_DB --fake my_first_app it correctly fakes my_first_app
The my_DB collation is case insensitive, while MySql is running with the ' --lower-case-table-names=0' option

[Hasan Ramezani]

Not sure about the solution.
PR just created for proposing the solution.

[Simon Charette]

Left a few comments for improvements.

[Mariusz Felisiak <felisiak.mariusz@…>]

In d0c86a1d:

Refs #29808 -- Optimized MigrationExecutor.detect_soft_applied().

Use set() for iterables used only for containment checks. Simplify
column checks O(n) instead of O(2n).

Thanks Simon Charette for an idea.

[Mariusz Felisiak <felisiak.mariusz@…>]

In 530dd19:

Fixed #29808 -- Fixed initial migration detection when identifiers are case-insensitive.

Thanks Simon Charette for the review.

[GitHub <noreply@…>]

In 4527d5db:

Refs #29808 -- Fixed MigrateTests.test_migrate_fake_initial_case_insensitive() crash on Oracle.