How to remove thumbnail and node in database when I remove the image?

I run this sample and it work fine. However, i want to remove a thumbnail and a node in the database when I deleted the origin image. Someone can help me, please. I try to search for a day but I can't get the solution :(

The issue does not identify the sample, files, tests, or entry points involved. First locate the image-upload sample and trace how the original image, thumbnail, and database node are created; done means deleting the original image also removes the related thumbnail and database node.

Written by the indexing model from the issue text.