Gaute Hope <eg at gaute.vetsj.com> writes: > A db-tick or a _good_ ctime solution can as far as I can see solve both > David M's (correct me if I am wrong) and my purposes, as well as > probably have more use cases in the future. It would even be an > interesting direct search: show me everything that changed lately, > sorted.
I could live with a db-tick scheme. I would prefer a ctime scheme, since then I can answer questions such as "what has changed in the last five minutes"? I mean all kinds of other stuff starts to break if your clock goes backwards on a mail server machine, not the least of which is that incremental backups will fail silently, so you risk losing your mail. A middle ground might be to use the maximum of two values: 1) the time-of-day at which notmuch started executing, and 2) the highest ctime in the database plus 100 microseconds (leaving plenty of slop to store timestamps as IEEE doubles with 52 significant bits). Since the values will be Btree-indexed, computing the max plus one will be cheap. Incidentally, if you are really this paranoid about time stamps, it should bother you that notmuch's directory timestamps only have one second granularity. It's not that hard to get a new message delivered in the same second that notmuch new finished running. In my synchronizer, I convert st_mtim (a struct timespec) into a double and keep that plus size in the database to decide if I need to re-hash files. But for directories, I'm stuck with NOTMUCH_VALUE_TIMESTAMP, which are quantized to the second. (Ironically, I think Xapian::sortable_serialize converts time_ts to doubles anyway, so avoiding st_mtim is not really helping performance.) David