Tribler becomes unresponsive with a large tags.db

[devos50]

Describe the bug
When using Tribler with a large tags.db (mine is 4.58 GB), Tribler becomes unresponsive fast, and everything blocks when doing searches/browsing through channels.

To Reproduce
Steps to reproduce the behavior:

1. Search for some content, like 'ubuntu' and scroll down. I noticed that the first request to /search completes pretty fast, but scrolling down in the list of search results and loading the subsequent batches is very slow and blocks the Tribler core entirely.

Expected behavior
Tribler should remain responsive with a large tags.db.

Desktop (please complete the following information):

• OS: macOS Monterey 12.3
• Tribler's version [e.g. 7.10.0]: latest commit on main branch.

[devos50]

I managed to track down the performance bottleneck to the get_tags_operations_for_gossip method. Returning [] from this call to sidestep the database query makes Tribler responsive again.