Thumbnail cache randomly rebuilds from scratch in folders set to thumbnail view (400x400) — no apparent trigger

[doggiejun]

Hi,
I'm experiencing a random thumbnail cache rebuilding issue that I cannot reproduce consistently.
My setup:
XYplorer version: 28.00.0600
Windows 10 (clean reinstall tested, issue persists)
Video files located on a HDD
XYplorer program and thumbnail cache located on SSD
Cache path: absolute path (not relative)
Cache size limit: 1000MB (current usage is well below the limit)
Settings confirmed:
"Cache thumbnails on disk" ✓
"Include local disks" ✓
"Create all thumbnails at once" ✓
Windows Storage Sense is disabled
The problem:
The thumbnail cache randomly rebuilds from scratch. This happens the moment I open a folder — the rebuild starts immediately upon entering.
This only occurs in folders where the view is set to thumbnail mode at 400x400 size. I have not tested other thumbnail sizes. The affected folders contain a large number of short video files, ranging from a few hundred to several thousand files per folder.
This does NOT happen every time. It occurs randomly — sometimes once every few days, sometimes twice in one day — with no obvious trigger. I frequently add and delete files in these folders, but that does not cause the rebuild.
Forcing shutdown does not cause the issue either. The rebuild happens at completely unpredictable times.
All thumbnails generate successfully after each rebuild. There are no files with permanently missing or broken thumbnails.
Additional notes:
I have reinstalled Windows and also tested with a fresh 30-day trial version of XYplorer. The issue occurs in both cases, which rules out a system-specific problem.
Is this a known issue? Could it be related to the 400x400 thumbnail size or the large number of video files? Any suggestions would be greatly appreciated.
Thank you.

[admin]

It's not a known issue. Let's see what could be causing it, step by step:

By default, the cache is rebuilt for files where the modified date has changed. To rule out this possible cause of your issue, set this tweak:

Code: Select all

CacheIgnoreModified=1

How to tweak: https://www.xyplorer.com/faq-topic.php?id=tweak

[doggiejun]

It's not a known issue. Let's see what could be causing it, step by step:

By default, the cache is rebuilt for files where the modified date has changed. To rule out this possible cause of your issue, set this tweak:

Code: Select all

CacheIgnoreModified=1

How to tweak: https://www.xyplorer.com/faq-topic.php?id=tweak

Hi admin,
​Thank you so much for your previous guidance! I applied the CacheIgnoreModified=1 tweak on June 7th as you suggested.
​Initially, this solution seemed absolutely perfect. Folders containing thousands of short video files were able to display all their thumbnails flawlessly, without any reloading.
​However, today (June 20th), exactly two weeks later, the thumbnail cache rebuilding issue reoccurred. The interesting part this time is that it did not affect all folders; only a few specific directories experienced a reload upon entry, while others remained perfectly cached.
​Since CacheIgnoreModified=1 is already active, we can definitely rule out the "Modified Date" as the culprit. Could you please help me look into this further to see how we can optimize this behavior? My ultimate goal is to permanently lock/solidify the thumbnail cache so it never triggers a rebuild unless done manually.
ps：My system has no third-party antivirus software installed, and I have not run any system cleaning or optimization utilities at all.
​Thank you again for your amazing support and for creating such an incredible tool!

[admin]

One possible reason, though unlikely, is: A rebuild can be caused by a corrupt cache. This can occur when multiple instances of XYplorer are running simultaneously and all use the same cache.

A solution: If you're happy with your cache(s) you can check "Configuration | Preview | Thumbnails | Show cached thumbnails only". That should prevent any rebuild.

[leonardo8]

For me also the rebuild occurs for jpg's(folder has less than 200 jpg's) once in every few days sometimes even if no new files are added to the folder,have not run xy simultaneously not even once

[doggiejun]

One possible reason, though unlikely, is: A rebuild can be caused by a corrupt cache. This can occur when multiple instances of XYplorer are running simultaneously and all use the same cache.

A solution: If you're happy with your cache(s) you can check "Configuration | Preview | Thumbnails | Show cached thumbnails only". That should prevent any rebuild.

Hi admin,
​Thank you for the quick reply and the suggestion!
​To help narrow this down, I wanted to share a bit more about my environment: I actually only run a single instance of XYplorer (64-bit) and do not use the dual-pane layout. It seems my environment might be experiencing this without the multiple-instance conflict.
​Also, I checked my actual cache folder and noticed that the total size has now reached 2GB. Inside, the largest .dbits file is about 1GB, and the rest is made up of smaller files. I wanted to share these numbers with you just in case they are relevant to how the cache behaves over time.
​Regarding the "Show cached thumbnails only" option, it unfortunately doesn't work well for my daily workflow. My folders are quite dynamic—I frequently add new video files to these directories or delete old ones. With this option enabled, newly added files will not show any thumbnails at all, which is a major drawback for me.
​Is there perhaps another tweak or setting that could help keep the existing cache stable for dynamic folders, while still allowing updates for newly added files?
​Thank you so much again for your patience and for looking into this with me!

[admin]

The next beta will have some debug code.