... btw, I think there is another problem here, which is that
generate_wildcard_trgm will restart get_wildcard_part at the
same place that the second loop exits, which means it would
do the wrong thing if what it returns is a pointer to the
second char of an escape pair. Consider for instance
foo\\%bar
The first call of get_wildcard_part will correctly extract "foo",
but then return a pointer to the second backslash. So the second
call will think that the % is escaped, which it is not, leading to
a wrong decision about whether to pad "bar".
Probably a minimal fix for this could be made by backing up "endword"
one byte before returning it if in_escape is true when the second
loop exits. That would not scale up to preserving the state of
in_wildcard_meta, but since the second loop never advances past a
meta char, that's okay for the moment.
regards, tom lane