Vaadin 7.4.0.beta3: Grid cannot handle data > 500k, column header no divide

I have a 600K or to be more larger database, Grid can show around 400k data, but the scroll bar become missing when my database size is around 600k data. Cannot scroll down even use keyboard. Just show the first available rows. I’m using Firefox 35.0.1.

And another one thing is the header column cannot be expanded. When the string is longer than the column space, I cant drag header column divider like the Table… Is it design like that? Or more api would coming?