schema-design

I have a Django project where I would need two models to have a foreign key to each other. However this is not possible because two Python files would have to import each other which Python doesn't allow. What is the best way to solve this problem? So my code currently looks like this: countries/models.py: from django.db.models import Model, ForeignKey from users.models import Profile class Country(Model): president = ForeignKey(Profile) users/models.py: from django.db.models import Model, ForeignKey from countries.models import Country class Profile(Model): citizenship = ForeignKey(Country)

Let say we have user and post collection. In post collection, vote store the user name as a key. db.user.insert({name:'a', age:12}); db.user.insert({name:'b', age:12}); db.user.insert({name:'c', age:22}); db.user.insert({name:'d', age:22}); db.post.insert({Title:'Title1', vote:[a]}); db.post.insert({Title:'Title2', vote:[a,b]}); db.post.insert({Title:'Title3', vote:[a,b,c]}); db.post.insert({Title:'Title4', vote:[a,b,c,d]}); We would like to group by the post.Title and find out the count of vote in different user age. > {_id:'Title1', value:{ ages:[{age:12, Count:1},{age:22, Count:0}]} } > {

One-to-one relationship could usually be stored in the same table. Are there reasons not to store them in the same table? Number and type of columns. There is a limit on the size of the columns in a table. See here . There is a maximum of 8,060 bytes per row. Very large tables can also affect performance and can be difficult to optimize and index well. This is apart from keeping data the is conceptually different, apart from each other. For example, a country and currency have a 1 to 1 relationship (illustrative example, I know this is not always the case). I would still not keep them together