Paperclip - how to display images that were not uploaded?

I’m using Paperclip plugin to store images in my application.

In the database I have columns like: image_file_name,
image_content_type, image_file_size.

When I upload an image via form, everything works well. But when I put
filename directly into the database and place properly named image in
the place expected, the image doesn’t appear on the webpage. Even if I
just rename uploaded file and accordingly change the name in the
database - it disappears from the view.

Why Paperclip behaves that way? Is there any other place where Paperclip
stores info about filenames and it’s loosing consistency when the names
are changed? So how to display images that have never been uploaded? (I
need it to display images from the old database and old image storing
system)

Ok, I found solution. I just must not to write file names directly into
database. When I place a file in the proper place it is displayed in the
view.