Database vs Data Structure?

[erikcw]

Hi,

I'm working on a web application where each user will be creating
several "projects" in there account, each with 1,000-50,000 objects.
Each object will consist of a unique name, an id, and some meta data.

The number of objects will grow and shrink as the user works with
their project.

I'm trying to decided whether to store the objects in the database
(each object gets it's own row) or to use some sort of data-structure
(maybe nested dictionaries or a custom class) and store the pickled
data-structure in a single row in the database (then unpickle the data
and query in memory).

A few requirements:
-Fast/scalable (web app)
-able to query objects based on name and id.
-will play nicely with versioning (undo/redo)

Any input on the best way to go?

Thanks!
Erik