The RaidNode policy file can have layered policies that can cover a file more than once. To avoid processing a file multiple times (for RAIDing), RaidNode maintains a list of processed files that is used to avoid duplicate processing attempts.
This is problematic in that a large number of processed files could cause the RaidNode to run out of memory.
This task proposes a better method of detecting processed files. The method is based on the observation that a more selective policy will have a better match with a file name than a less selective one. Specifically, the more selective policy will have a longer common prefix with the file name.
So to detect if a file has already been processed, the RaidNode only needs to maintain a list of processed policies and compare the lengths of the common prefixes. If the file has a longer common prefix with one of the processed policies than with the current policy, it can be assumed to be processed already.