Question

Is there any way in mongoid to find and ‘read’ all documents in a collection while also removing them in one, atomic query?

So far I was using:

Model.collection.find().to_json
Model.delete_all

Which can be easily broken by adding more data to collection between those two instructions.

Answer 1

You could, for example, rename the underlying collection to something like tmp_cf20c448f824763454ada2c4b2434178. Then all new writes will go to a new, automatically created collection with old name, and you can, without haste and worries, read all documents and then simply drop that temp collection.

This kind of stuff is usually done more easily using the underlying ruby driver (10gen’s mongo for mongoid 2.x or moped for mongoid 3.x).