Extending django.contrib.auth.models Group name to be 191 character max_length

[Tim Allen]

Greetings,

Over the past few releases, several CharFields in django.contrib.auth have been increased to a max_length of 191: username, first_name, and last_name immediately come to mind.

See: https://groups.google.com/forum/#!msg/django-developers/h98-oEi7z7g/xzjtFMf1BwAJ

I've issued a PR to extend Group.name to the same length here: https://github.com/django/django/pull/10627 The original ticket this is addressing was from a colleague who was bumping into the limit when syncing groups to Django from LDAP: https://code.djangoproject.com/ticket/29939

The 191 character limit was chosen to support MySQL index limits.

Can anyone think of a reason not to change Group.name to be max_length=191 as we have with the other fields?

Regards,

Tim

[joh...@alumni.upenn.edu]

If the other fields are also 191, i see no reason not to make the change.  It should be a non-breaking change.  And Yes i am that colleague...

[Aymeric Augustin]

That seems all right to me.

-- 

Aymeric.

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[Carlton Gibson]

(Before I start, I'm +1 but... 🙂)

Just having a quick go over the history here...

* Original discussion floated a change to 100 or 150 chars. 

    * Aymeric valued fixing the issue for 99.999% of cases. 

    * Tom Christie wanted an "human value", not a machine one. 100 chars was suggested. 

    * Florian said 150 chars, still human, a bit longer. 

    * This didn't get resolved. 

* https://code.djangoproject.com/changeset/15ef1dd478c5b6f005e5f782b7619f718ed55e84 set the limit to 254 chars for User.username.

* Comment at https://code.djangoproject.com/ticket/20846#comment:25 begins, "This patch breaks on MySQL..." — some discussion of using 191 chars. 

* Eventually https://github.com/django/django/commit/780bddf75b93784470a2e352ed44ee35a751d667 reduces the limit to 150 chars. 

* https://github.com/django/django/commit/d5b573d872bbe0d5825efaee2d41cb3cdc75417b follows suit (to 150 chars) for `last_name`

Current state of play is that username and last_name are 150 chars. first_name is still 30 chars. 

https://github.com/django/django/blob/ff8020ed49571b0fece67d10d7398d5f57cbaa74/django/contrib/auth/models.py#L288-L308

I don't know what's going on with first_name but I think 150 chars is the go-to value here. 

(Hey, nice 🚲 🙂)

Regards,

Carlton

[Tim Allen]

I've amended the PR to be 150 characters rather than 191.

Thanks for doing the digging which explains why I had 191 characters stuck in my head. I'm in the "as long as possible to cover the most possible cases" camp, but 150 would seem to hit the 99.99999%, so let's call it a win! 

🎉

Regards,

Tim