Hi Max, > Please, avoid mixing of system clock and filesystem timestamps. > > (file-attribute-modification-time (file-attributes file)) > > should be more reliable.
Thanks for the tip, I’ve updated the patch to use this. > In general, I would prefer to avoid relying on timestamps at all, but I am not > sure if it is possible to implement in elisp with reasonable efforts. The idea > is to save into file header a hash of content (or a random number). To check > if file has not been modified, just header is read at first. If hash does not > match the value stored in memory then it is necessary to read the whole file. The current approach is certainly sub-optimal, but it’s also simple and unlikely to cause any issues in practice. > Another point that I am unsure is if Emacs ensures file locks. If one emacs > process writes disk cache file then attempts to read the same file by other > emacs instances must be postponed. I’m not sure, but you’d need two Emacs instances to try reading/writing the index file at near-/exactly/ the same time, which seems vanishingly unlikely. > Cooperation in respect to disk cache would be an improvement, but it may be > tricky to implement it reliably. We could just write more often and run `org-persist--merge-index-with-disk' with some heuristic during operation (if the file is unmodified since it was last checked nothing will happen). However, I think that’s probably best left to another conversation — let’s not allow perfect to be the enemy of good here 🙂. All the best, Timothy -- Timothy (‘tecosaur’/‘TEC’), Org mode contributor. Learn more about Org mode at <https://orgmode.org/>. Support Org development at <https://liberapay.com/org-mode>, or support my work at <https://liberapay.com/tec>.
