Vaadin has a nice concept of lazy loading data in most of the components.
For example the table, list, dropdown's etc. have that concept.
The only thing you realy need to know at start, is the number of total rows.
Everything else can then be handled "ondemand".
For example the Table component initially only loads about 30 rows (can be customized)
and then fetches rows as needed. (Or better they are usually fetched just before the user scrols to the next rows)
A example is this demo
http://demo.vaadin.com/dashboard/#!/transactions
How you retrieve the data from your backend depends on the technology used.
But vaadin has working concepts where you don't need to load all 1mio. rows into memory,
it will handle the "fetch on demand" as the rows need to be displayed.