3.5 Inodeprints

Fairly often, in order to accomplish its job, monotone has to look at your workspace and figure out what has been changed in it since your last commit. Commands that do this include status, diff, update, commit, and others. There are two different techniques it can use to do this. The default, which is sufficient for most projects, is to simply read every file in the workspace, compute their SHA1 hash, and compare them to the hashes monotone has stored. This is very safe and reliable, and turns out to be fast enough for most projects. However, on very large projects, ones whose source trees are many megabytes in size, it can become unacceptably slow.

The other technique, known as inodeprints, is designed for this situation. When running in inodeprints mode, monotone does not read the whole workspace; rather, it keeps a cache of interesting information about each file (its size, its last modification time, and so on), and skips reading any file for which these values have not changed. This is inherently somewhat less safe, and, as mentioned above, unnecessary for most projects, so it is disabled by default.

If you do determine that it is necessary to use inodeprints with your project, it is simple to enable them. Simply run mtn refresh_inodeprints; this will enable inodeprints mode and generate an initial cache. If you ever wish to turn them off again, simply delete the file _MTN/inodeprints. You can at any time delete or truncate the _MTN/inodeprints file; monotone uses it only as a cache and will continue to operate correctly.

Normally, instead of enabling this up on a per-workspace basis, you will want to simply define the use_inodeprints hook to return true; this will automatically enable inodeprints mode in any new workspaces you create. See Lua Reference for details.