Oracle PL/SQL decryption function breaking index?
I've found that the reason that decryption xor sorting is fast, but decryption and sorting is slow:


Decryption will only grab the first 100 or so records, decrypt them, and display them.  Fast.
Sorting will grab the first 100 or so records (utilizing the pk index) and display them.  Fast.
Decryption and sorting will force a table scan, resulting in decrypting several thousand records, and then sorting them all.  


In other words, the "fast" queries are only fast because they're doing very little work.