Not really, and duckdb doesn't need to hold everything in RAM as i recalll. But it's fast, far faster than several read-process-write steps can be, especially when coordinated over multiple machines

(By the way, maybe I was vague, using overloaded terminology. To be precise with 'in-core' i meant that the solution to an analytic query is held completely in memory, not that it's restricted to using one cpu thread.)