Increase the max_length of Redirect.old_path/new_path

[s.shanabrook@…]

In django.contrib.redirects the the old_path and new_path have max_length=200. This presents problems when either of the paths has a longer length than 200. URLField used to have a max_length=200, but this was resolved [1477] and isn't even applicable, since the path fields use CharFields, not URLfields.

I would recommend a max_length=2000. URL's with a length over 2000 are ​not as well supported. However since ​database enforcement of CharFields in MySQL is limited to 255 characters, the fields have to be also changed to TextFields.

[Saul Shanabrook]

Created fix at ​https://github.com/saulshanabrook/django/tree/ticket_19515

[Aymeric Augustin]

Thanks for the suggestion. The problem here isn't to change the max_size — it's to provide a suitable upgrade path for existing users. Otherwise, application-level and database-level constraints won't match any longer, which will result in uncaught errors.

In general we've postponed this kind of requests to after Django gets built-in migrations — most likely 1.6 or 1.7.

(By the way a CharField is fine. We don't need a textarea to copy-paste an URL.)

[s.shanabrook@…]

Even though we don't need the form provided by a CharField, MySQL limits unique Charfields to 255 characters:

​https://docs.djangoproject.com/en/dev/ref/databases/#character-fields

"Any fields that are stored with VARCHAR column types have their max_length restricted to 255 characters if you are using unique=True for the field. This affects CharField, SlugField and CommaSeparatedIntegerField."

[Gavin Wahl]

Django now has built-in migrations. Is this feasible now?

[Tim Graham]

I'd think so (hence why I moved the ticket to accepted).

[Claude Paroz]

This will be far easier once #28661 is fixed.

[Mariusz Felisiak]

Blocked by #28661.