Hi!
This one comes from C++'s `std::string_view`: being just a `const char*`
plus the `size`, it's a very convenient type to use in interfaces which
don't need an ownership of the data passed in.
Unfortunately, `PQfnumber` expects a null-terminated string, which
`std::string_view` can not guarantee, and this limitations affects the
interfaces built on top of libpq.
Would you be willing to review a patch that adds an `PQfnumber` overload
that takes a `field_name` size as well?