Programatically is it possible to list up all the path aliases that my site has?
I got a fresh installed d8.1 and a fresh pathauto 8.1.x-dev.
I got the url_alias table in my database by installing the module.

the table schema is [pid | source | alias | langcode]

I guess what you want to do is something like this:

$query = db_select('url_alias', 'ua')
  -&gt;fields('ua', array('alias'))
  -&gt;execute(); 


that should give you the result you want.