Feat: --skip-content-hash, --max-prefix-size, --max-suffix-size options #202
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- dirs 4.0 -> 5.0.1 - fallible-iterator 0.2 -> 0.3 - sysinfo 0.28 -> 0.29 - Required renaming DiskType to DiskKind in various places
--max-prefix-size - Configurable byte-size parameter for the max length of a file to hash for prefix checking --max-suffix-size - Same as --max-prefix-size, but for the suffix check
--skip-content-hash will skip the final stage, returning the results from the previous groupings as the final result. This can speed up the checking byorders of magnitude on large files, and alongside --max-prefix-size and --max-suffix-size, can still provide reasonable guarantees on whether files are duplicates.
pkolaczk
approved these changes
Jun 4, 2023
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Partially fixes: #201
(Completely open to changes in the naming/wording/api/etc.)
Changes
--max-prefix-sizeand--max-suffix-sizeoptions--skip-content-hashoption--transform)Potential Follow-up
Random chunk checks:
--random-chunk-checks=5--random-chunk-size=16MiBThough prefix and suffix size checks are a great pre-filtering step, they are of course the parts of the file that would seem the most likely to be the same among different files. However, there are still cases where fully-hashing the file would take a prohibitively long time or be too expensive.
Instead of a full hash, we could use the file's byte-size as a seed to randomly select
nchunks to read from and group in the same fashion as the prefix and suffix checks. Doing this should make it very unlikely for duplication while still being orders of magnitude faster than full content hashing. It also has the nice side effect of being a great continuous tuning-lever to find a balance between safety and speed.