There are quite a lot of errors in just one sentence:
First of all, "Glock 7" doesn't exist, Glock never had a model with that number. First Glock pistol was Glock 17 ("The Gun Digest Book of the Glock"
By Patrick Sweeney, chapter 9). Glock is Austrian, not German company.
The purpose of non-metallic gun would be to not be detected via metal detectors, rather than X-ray machines, which can detect any dense object, regardless if it's metallic or not. ( "FBI Guide to concealable weapons" features quite a few examples of non-metallic knifes undetectable by magnetometer, clearly visible on X-ray).
Movie gun is most likely inspired by Glock 17, which was one of the first guns to have polymer (i.e. plastic) body. However, barrel, chamber, spring and all the rest of firing mechanism is metal. And of course standard pistol ammo is metallic (both bullet and jacket).
Porcelain gun is just ridiculous. I'd assume someone wanted to say ceramic. Porcelain is a ceramic made of kaolin clay, however there are quite a lot other ceramics, which would be apt for making weapons parts. Especially when combined with other materials creating ceramic composites.
There are companies specializing in customizing weapons, which offer carbon-fiber/ceramic barrels (example), but even these internally have steel lining. However, currently there is not a single company, which would have non-metal firing mechanism on the market.
There are rumors of secret research to develop all-ceramic gun, however there isn't even a shred of hard evidence that it was actually done.
As for hypothetical possibility, making fully functional ceramic gun most likely wouldn't be economically feasible. Perhaps given enough resources I imagine that very crude improvised gun such as "pen gun", could be made w/o metal. However "pen gun" isn't what one would call fully functional firearm. See Discovery's "Son of Guns" "Alligator Kill Stick" episode to see how such a "pen gun" works. However, they of course use metal.