It will work just fine. A G19 has a 4inch barrel just like the SD9VE. Look on Amazon even at the G19 guide rods and you can read lots of reviews of people buying them for there SD9VE and saying they work perfect.
I have replaced the stock guide rod with a Glock 19 guide rod and the gun performs perfectly. It fit the SD9VE and functions as advertised, at half the cost.