I'm getting unexpected behaviour from this search:
when using #r (my lookup name for the custom column containing the grrating identifier),
#r:false returns 0 titles; whereas using identifiers:grrating:false the search returns the correct number of titles in the library that still don't have the grrating.
OTOH, both identifiers:grrating:true and #r:true queries return the titles that already have the grrating, as expected.
not sure if this is a PI issue
(i've tried renaming the custom column from #r to #gr, but that didn't help: searching for #gr:false returns a empty list)