Relating to thumbnail and category

[minhngq]

Hello,
I am very happy with XnView MP after switching from other software. I have some suggestions for improving: (i) the performance of rendering thumbnails and (ii) managing categories in both files & folders. Please feel free to discuss.
The assumption here is that on user's PC, there are a lot of folders and files (photo, video).
1. Thumbnails:
- I observe that the thumbnails are all stored in a ".db" file and it gets very big overtime causing the app takeing (much) longer time to render cached thumbnail or even worse re-build thumbnails when browsing folders.
- Is it OK to maintain multiple thumbnail-cached files and the main ".db" file serve as indexing/routing database? This is similar to sharding technique found in database server where each thumbnail-cached file is "one shard". The shard can be either store at XnView configure folder or attached to each photo/video folder (like what windows explorer does).
- And if the shard is attached to folder, it is very fast/convenients for user to copy/move folder to new location (outside XnView MP app) with thumbnails. Later on, just re-index the thumbnail file in the main ".db" file.
- In this way, maintenance tasks (append, remove, browse) become more efficient.
2. Managing categories, I have 2 suggestions:
+ 2a. Sidecar for "Category on folder":
- Currently XnViewMP allows for applying categories on each folder. But there is no sidecar for folder (like xmp file for photo). So if user move, copy folder to new location using other application (windows explorer,...), all category settings are lost. One of the use-case for using different application for copying/moving is when that folder comes from network share (in the NAS device); doing file operations on remote machine is much faster.
- So, I strongly request to have sidecar or similar method in this scenario.
+ 2b. Synchronizing category between sidecar and XnView MP's database
- I would suggest to have specific feature to synchronize (2 ways) between sidecar and XnView MP's database. User should pick a list of folder (or the whole drive), then XnView scans the sidecar, imports to its database or vice versa.
- And if you do have distributed thumnail-cached file like in suggestion 1; this feature also includes the thumbnails.

Thank you.