Improve iterators

[Altahrim]

Ref #507

[blizzz]

Please don't forget to set the milestone when opening a PR 😃

[tovine]

What's the outlook on the timeline for this one? I just had an update basically time out and break itself when I decided to look at the updater code - only to find out that it recurses through all files (including user data and old backups) before doing the filtering.
My server is basically stuck at creating backup for an hour, with the apache process disk-limited at 2% CPU usage and about ~250kB/s read. This pull request looks like it should fix all that and make updating Nextcloud bearable again... 🙏

[Altahrim]

No timeline as I don't find time to work on this…
As a workaround you can do a backup manually and use the --no-backup option in the updater

[doits]

As a workaround you can do a backup manually and use the --no-backup option in the updater

Even with this flag it still hangs/iterates at "Delete old files ..." unfortunately, so it is only a partial solution. (My updates take 1+ hour, too.)

[tovine]

No timeline as I don't find time to work on this… As a workaround you can do a backup manually and use the --no-backup option in the updater

Understandable.
Is there much left to be done or is it just a matter of testing?

[doits]

My last update from 29.0.1 to 29.0.2 was much faster though (still with --no-backup)! Only took very few minutes for the "Delete old files ..." step (didn't pay attention to exactly how long because I thought it will run for 1+ hour but it finished much much quicker). Coincidence or was something merged between those releases that made this much faster? I'm puzzled.

[tovine]

Is there a way I can test this fix on my own instance? Looks like the change should work and be safe enough so I'd like to give it a try if possible