Block statistics per Adlist

I'm rather new to Pi-hole and I'm currently experimenting with various blocklists.

Is there any way to identify the number of block per adlist? Or how do you decide whether an adlist is good or useful?

Advertising my own script

Seems like this would be exactly what I had in mind, but I'm afraid I run into the same error, as someone mentioned on your github page yubiuser.

Error: database is locked

I've tried running the script as my default user and root, same result. My Pi-Hole has only been running for two days, so not much there to process yet.

I manually copied the two database files and changed to script to use the copies instead. I don't get the error with the copies, but no results either, after more than 20 minutes (RPi3 4x 1.2 GHz, 1GB RAM).