Selection in files with many objects Selection seems to work in wierd ways. I have a 3D File with ~4.000.000 Tris and ~120.000 Objects. The file results from a CAD software and needs to be further processed.

My idea was splitting the File in smaller parts because opening it takes minutes and the viewport is very laggy. But the real problem is that simple things like selecting parts of something take ages (for larger areas minues) and give not the expected results. (100% one CPU-core the others idling - The machine isn't the problem)

Has someone tips for working with files like this?


Edit:
Selectable parts seem to be consitend till i moving the selectet parts to a different layer (takes minutes to finish). After that other parts become selectable.
Here are a couple of things, you might want to try (actually, this is more of a comment than an answer, but I haven't earned privilege to make comments yet).


Selections in outliner (the right hand side panel) are much faster than in the 3d area. 
You can try hiding other objects with Shift+H (Alt+H to clear).
Alt+B will allow you to select a small portion (box select) to work in edit mode. You can switch back to the normal mode by pressing Alt+B again.