Performance issues with initial sync and UI responsiveness

[minhthanhonly]

Which Nextcloud Version are you currently using: 32.0.3 with Desktop Client 4.0.4 and with Windows 11.

When syncing a large number of files (>100k), several performance problems occur:

1. Initial sync too slow

• Problem: First-time sync with very large file counts takes an extremely long time.
• Suggested solutions:
  • Implement lazy sync — only sync folders when accessed.
  • Cache or save a file database of folders to reduce the overhead of counting and reading each file.
    ・Users connecting for the first time could simply download the saved database instead of recalculating everything.

2. UI becomes laggy during sync

• Problem: The Nextcloud UI is noticeably unresponsive while syncing files.
• Suggested solution: Move sync operations to a separate thread so the UI remains smooth.

3. File counting takes too long

• Problem: Counting the number of files to sync consumes excessive time.
• Suggested solution: Optimize or defer file counting to improve responsiveness.

[minhthanhonly]

Counting ~600,000 files took 2 hours.
It took 24 hours to upload everything. (500GB)