Case insensitive uniqueness

[wojcikstefan]

from mongoengine import *

connect('dbname')

class A(Document):
    b = IUniqueStringField()

c = A()
c.b = 'whatever'
c.save()

d = A()
d.b = 'WhatEVER'
d.save()

results in:

(env)[mongoengine] python test.py                                                                                                                             19:00:59 git:(master*)
Traceback (most recent call last):
  File "test.py", line 11, in <module>
    c.save()
  File "/Users/wojcikstefan/Repos/mongoengine/mongoengine/document.py", line 266, in save
    raise NotUniqueError(message % unicode(err))
mongoengine.queryset.NotUniqueError: Tried to save duplicate unique keys (E11000 duplicate key error index: tumblelog.a.$_b_lower_1  dup key: { : "whatever" })

[rozza]

Not 100% sold on this one - Maybe I'd be happier if it was a custom field - then we could be more explicit about the costs of this approach.

[wojcikstefan]

@rozza I changed it to be a custom field. How do you like it now?

[rozza]

Looks good! I think this should go into: https://github.com/MongoEngine/extras-mongoengine

The fields themselves need docs and then we need a generic way to hook into mongoengine/base.py and do modifications there.

What do you think?

[wojcikstefan]

Hey Ross! You're right, extras-mongoengine looks like a more suitable place for these fields. Feel free to close this PR, I'll make a new one in the other repo.

[wojcikstefan]

Having given it more thought, I'm afraid that moving these changes to the other repo is non-trivial. I'd have to override the original DocumentMetaclass in extras-mongoengine and then you'd need to specify my_metaclass and __metaclass__ in the document, in which you'd wanna use the above fields. Seems like a big hassle.

Am I not seeing an obvious, easier solution?

[rozza]

I think we'd need to include some sort of hook in mongoengine to call from the field class. Let me ponder it :)

[wojcikstefan]

@rozza, just following up - how's the pondering going? :) I would like to implement something like this in one of my projects very soon and am wondering whether to wait for the upstream changes or change my fork.

[wojcikstefan]

Came up with a simpler implementation that can be easily included in https://github.com/MongoEngine/extras-mongoengine. I'll open a PR there soon.

[coveralls]

Changes Unknown when pulling 80cbe9d on elasticsales:case-insensitive-uniqueness into * on MongoEngine:master*.