kv_revisions.py

from django.db import transaction
from django.db import models


class Collection(models.Model):
    name = models.CharField(blank=True, max_length=100)
    revision = models.IntegerField(blank=True, null=False)

    @transaction.atomic
    def save(self, items_dict, *args, **kwargs):
        if not self.revision:
            self.revision = 1
        else:
            self.revision += 1

        ret = super(Collection, self).save(*args, **kwargs)
        self.save_items(items_dict)
        return ret

    def save_items(self, values_dict):
        CollectionItems.objects.filter(collection=self).update(latest=False)

        for k, v in values_dict.items():
            CollectionItems.objects.create(
                key=k,
                value=v,
                revision=self.revision,
                collection=self
            )


class CollectionItems(models.Model):
    collection = models.ForeignKey(Collection)
    revision = models.IntegerField(blank=True, null=False)
    key = models.CharField(blank=True, max_length=100)
    value = models.TextField(blank=True)
    latest = models.BooleanField(default=True)



# CollectionItems.objects.filter(latest=True, key='tag', value='Foo')