So you're going to an underpowered machine (8gb is half the memory my laptop has) and you're running a very large aggregation query and returning 1.7 million rows. The machine is expected to both process the query and then process and display the result set, but you're unsure why that's causing the system to slow down? I'm pretty sure I can tell you why. Think about it, the result set isn't just stored once. It's being processed by the server instance and then it's being processed by the client, both on the same machine. Plus, I'll be you don't have max memory set inside of SQL Server. So the server instance is chewing up as much of the memory resources as it possibly can to answer your query. Then, the OS has to try to either reclaim a bunch of that memory form SQL Server in order to store it within the client application of SSMS (which isn't using the same memory space as your SQL Server instance, they are two completely separate executables) or, it's swapping out to disk like mad in order to consume all that data.