From @dpoirier: Here's a stab at a script to fix up our Basket data given a set of email-token mappings.

dedupe_basket.py

# Draft script to fix the token mappings in the Basket database,
# given a list of valid email-token mappings

from django.db.models import Q

from news.models import Subscriber


# Let's assume we have the data in the form of a dictionary,
# where each key is an email address and its value is the corresponding
# token (or we can get it into that format).

# For an example, make up a dummy set of data
data = {
    'user1@example.com': 'c5586048-a640-4bb8-be63-3a8b06add858',
    'user2@example.com': '360f7283-d9db-4ecc-ae32-4082ef4b7d81',
}


# Let's just delete any existing records with either the email or token,
# then create one with the right mapping.

email_query = Q(email__in=data.keys())
token_query = Q(token__in=data.values())
Subscriber.objects.filter(email_query|token_query).delete()
# That was one query.

# Now create the right mappings.
# If we have Django 1.4 or later, we can do it in one more query.
if hasattr(Subscriber.objects, 'bulk_create'):
    Subscriber.objects.bulk_create(
        Subscriber(email=email, token=token)
        for email, token in data.iteritems()
    )
else:
    # We'll have to do it one at a time.
    for email, token in data.iteritems():
        Subscriber.objects.create(email=email, token=token)