Possible to "lock" device folders to be scanned?

[Moonbase59]

I usually configure my devices to only scan the "Books" and "Download" folders, to save time whenever the device is connected to Calibre via USB.

Unfortunately, whenever one adds folders, moves things around, or renames folders on the device, these will be automatically included in Calibre’s device folder scan, leading to enormous RAM waste and endless scanning times (especially when using Android MTP).

Just took me almost half an hour (!) until Calibre showed the books on my tablet, just because I had installed an additional reader and some new StarDict dictionaries that each contained thousands of images in their "res" folders.

So my question/feature request: Would it be possible to configure device folders to be scanned and then somehow "lock" that selection, so Calibre would not go and look for new folders/changes when connecting?

[kovidgoyal]

No, there isnt. Adding thousands of files to the Books folder is not likely to be a common occurrence.

[Moonbase59]

It’s not adding to the "Books" folder, but other random folders on the device, like "dictdata" or "koreader/data/dict/…". These get automatically checked.

So the actual process becomes:

• Connect device.
• Wait endlessly for Calibre to check all new unwanted folders.
• Go "Configure device" and untick all these folders.
• Restart Calibre, wait again.
• Desired result (only "Books" and "Download").

[theducks]

Originally Posted by Moonbase59

It’s not adding to the "Books" folder, but other random folders on the device, like "dictdata" or "koreader/data/dict/…". These get automatically checked.

So the actual process becomes:

• Connect device.
• Wait endlessly for Calibre to check all new unwanted folders.
• Go "Configure device" and untick all these folders.
• Restart Calibre, wait again.
• Desired result (only "Books" and "Download").

There are 2 files in the root that 'calibre' <hint> uses to 'log' previous scans for speedup. If you tamper with those, it has to start over.
I Shuffle my device (non-book) folder CONTENTS frequently with no rescan. Don't touch the path to known book folders.

[Quoth]

Create the folder/directory, but with no contents.
Connect to Calibre
Go to device settings
untick that folder/directory (new ones are ticked by default)
Now exit calibre
You can now put 1000s of files / subdirectories in that new empty one and Calibre won't scan them.

So when getting a new device with maybe 32G to 1000 G SD card, first create the empty top level directories and then connect to Calibre before adding the content.

[Moonbase59]

Yup, so much for theory (thanks nonetheless!). Only, if installing software on a device like a tablet, one doesn’t often check (or care) what folders it creates/uses.

In my case, I experimented with several dictionaries, KOReader, Librera, ColorDict and GoldenDict on my Android 4.4.4 Tolino Tab 8", to find which would work best with KOReader and Librera.

So I still think some restriction to device folders scanned might be useful. Or, as I proposed in the bug report below, an initial selection by the user before the scan starts.

I feel that—for inital scans—a restriction to the "list of folders on the device to which to send e-books" might be in order, to avoid scanning the whole device. After that, only scan what has been selected in "Change scanned folders" and don’t auto-activate each new folder detected.

Thinking about it, that’s what I meant when saying "lock folders": Don’t auto-activate new ones. That should solve all these problems. For those who wish for "everything fully automated", maybe a setting like "Auto-activate new folders on device for scanning (Y/N)?"

Related: https://bugs.launchpad.net/calibre/+bug/1943991 (Immense RAM usage due to scanning unneeded stuff; solved by manually editing mtp_devices.json.)