QuerySet count vs len

[marcoskv]

The MongoEngine documentation recommends to use len to count results, because it is more Pythonic.

count() executes a server side count query, while len() retrieves the results, places them in cache, and then counts them.

If we compare the performance of the two operations, len() is super slow compared to count().

It would be better to explain that properly in the documentation.

[mmellison]

Feel free to throw up a Pull Request for updating the documentation. We are trying to clean up our back log of issues but we currently have a lot of issues and bugs to work through. Any help would be appreciated. :)

[wojcikstefan]

The documentation around this is better now, making it clear that Doc.objects.count is the way to go.