You are in a confined aisle. If he is already moving towards you, you will not have time to draw your sidearm, even if you move straight back (which is a bad choice). You only gain time to draw and engage if you move off the "X"...which you cannot do in a confined space. Sooooo, without the ability to draw, you will likely have to go "hands on". While it is not prefered, it is quite possible to defend yourself against a knife attack with only your hands. After many FOF simgun scenarios with rubber knives, I've learned this lesson the hard way.
Am I accurate in thinking in the scenario you're describing, getting right up to the perp wrestling style lessens their ability to stab you?