Available inall subroutines.

This is a companion discussion topic for the original entry at https://developer.fastly.com/reference/vcl/functions/query-string/querystring-add

We ended up having to use

if (req.url.qs != "") {
    #a querystring exists
    set req.url = req.url "&amp";
} else {
    set req.url = req.url "?amp";

querystring.add will not add a querystring if the value is left empty.

set req.url = querystring.add(req.url, "amp", "");

The above code ends up doing nothing, instead of what we wanted it to do, which was add ?amp to the end of the url.