There's only 16Gb of RAM on this computer (quad-core 15" Macbook Pro) but Activity Monitor is saying mds_store is using 32Gb. Rendering in Sublime and Brave browser when I scroll and type was lagging considerably. It's been indexing for at least the last two days.
sudo mdutil -a -i off slowed the fan speed but the lag still persists, and Activity Monitory memory is still at 32Gb.
After that, I run
sudo fs_usage -w -f filesys mds_stores and I get a lot of Backup and Sync and Brave Browser with
/dev/disk1s4 /System/Volumes/VM/swapfile0. I quit Backup and Sync (using Brave to write this) and there's still no change to performance or memory.
Also, after upgrading to Big Sur, Spotlight basically useless since it's so slow.