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From: Timothy <orgmode@tec.tecosaur.net>
To: Max Nikulin <manikulin@gmail.com>
Cc: emacs-orgmode@gnu.org
Subject: Re: [PATCH] Merge loaded org-persist index with index file contents
Date: Sun, 11 Dec 2022 19:26:42 +0800	[thread overview]
Message-ID: <871qp6qipu.fsf@tec.tecosaur.net> (raw)
In-Reply-To: <tn4a4f$235$1@ciao.gmane.io>

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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>.

next prev parent reply	other threads:[~2022-12-11 11:33 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-12-11  7:59 [PATCH] Merge loaded org-persist index with index file contents Timothy
2022-12-11 10:07 ` Max Nikulin
2022-12-11 11:26   ` Timothy [this message]
2022-12-14 15:07 ` Timothy

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