Using Prune Filter To Remove Null Value Fields

[Badger]

No, blacklist_values takes a hash, each member of which is a field name and a regexp used to determine whether to remove the field. You can do it in ruby

    ruby {
        code => '
            event.to_hash.each { |k, v|
                if v.kind_of? String
                    if v == ""
                        event.remove(k)
                    end
                end
            }
        '
    }