I don't have an answer for you...
However, I did note that you are using PG. To that end, make sure to update the driver:
Boolean expression in search
is it possible to use Boolean operators to run advanced search queries in nodeBB search functionality?
As far as I'm aware this completely depends on the search plugin you're using.
You can use
orby changing the match words option in advanced settings. Mongodb also supports some other options like
"phpbb" -"nodebb"this would match topic titles that contain
nodebb, example search