GNOME has a built in local file search feature, which can be handy for casual users. But I have, just because of my own curiosity, a copy of the Linux kernel source code (96,000 files) and the Firefox browser source code (388,000 files) and a handful of other projects on my machine, and a shell script that updates the code from git every week.
So GNOME's file search just uses a lot of CPU power and a lot of disk space for nothing for me.
The solution, thanks to a kind soul on the fediverse:
systemctl --user mask --now localsearch-3
Then I deleted ~/.cache/tracker3/files (and the older
~/.cache/tracker/files.