This is pretty interesting. A while back, my buddy David sent me an email asking about the process of deleting files from his iPhone. He had deleted some mail messages and then gone to the search page and found the messages even though they were deleted.
Search page? iPhone OS 3.0 introduced a search page, to the left of the home page. Press your home button to bring you to your home page and either drag to the right or press the home button again. This brings you to your search page. Using Spotlight (reverse indexing), the search page searches everything stored on your iPhone. This includes music, email, apps, photos, and even the trash!
Giving the user the ability to search deleted files is an interesting choice on Apple’s part. There’s no way to restrict searches so deleted files are not searched. In addition, there’s no simple way to “really delete” files so they are scrubbed from the persistent store. Not really a problem, unless you’ve got sensitive material on your iPhone that you really want to delete.
Enter my buddy David again. We cooked up this experiment which he was nice enough to run. He deleted some emails, then searched for them and verified that search found them and that he was able to open the deleted emails by clicking on them in search.
Next, he built a giant playlist that consumed all the free space on his iPhone. The theory: Apple maintains a list of deleted items and returns the memory to apps as requested. When an app needs more memory, they get that memory from the deleted list once regular memory is used up.
David ran the experiment and, as expected, as he filled his iPhone, items disappeared from the deleted list. Pretty interesting. Try it yourself…