Merging time is very (very) long!

I’m using EF for five years now, and I experiment a way too long time when merging emails from Apple Mail. Every month, I do a import with the fn+F1 keystroke. But every month, I have to merge the “old” mailbox with the “last month” one. And it’s very, very long (3-4 hours, the longer operation is the indexation).
So this month, I tried to import just one email (ie eml format) and merge thinking it wont’ be so long : more than 2,5 hours… 15 minutes in rebuilding mailbox, 2,5 hours to reindex…
My mailbox contains 21240 emails. It’s on a external SSD drive (mailbox size : 2,7 Go). I’m using a MBP M1 Pro 16go.
Why is it so long ? Is there a way to avoid this ?
Thanks for your advice…

The way merging currently works is that it creates a whole new mailbox and a new index for it. This design was chosen because it works well with undo—the old mailbox and index are still there until you empty the trash. If there’s a storage problem or you change your mind, it’s easy to go back. The downside is that the rebuilding/indexing time will depend on the total size of the new mailbox rather than on the amount that was “added.” I plan to improve this in a future version.

That said, 21,240 e-mails is not that many, and I would not expect them to take hours to index. Is there other stuff happening in the Activity window at the same time? Do the e-mails have lots of attachments?

You can click here enable logging for message indexing and then, after it indexes for a while, send in a diagnostic report. That may provide some clues as to why it’s slow. The logging will slow things down a lot, though, so be sure to disable it by clicking here after we’re done troubleshooting.

Hi Michael,

I just sent it to you !

Thanks for your help !

Thanks. There is no obvious cause of the slowness, i.e. it does not seem to be getting stuck on any particular attachments. I will need to add some more instrumentation to investigate this, and some overall indexing speed improvements are also in the works, which I think will help.

OK, hope your further development will help, thank you !