Make .desktop file show up?

[Tom Horsley]

I was figuring out how to install an app, and made the .desktop
file for it and put it under /usr/share/applications, but it
didn't show up in the gnome 3 search till much later (maybe
after logout/login or reboot, I forget when I noticed it
was there).

Is there some magic incantation to make gnome-shell notice
new app .desktop entries right away?

Just curious.