Function run_statement_streaming 

pub async fn run_statement_streaming<T: StatementTransport, A: AuthProvider>(
    cx: &Cx,
    client: &T,
    auth: &mut A,
    request: SubmitStatementRequest,
    params: SubmitQueryParams,
    poll_plan: PollPlan,
    sink: &mut dyn RowSink,
) -> (StatementOutcome, DriverStats)

run_statement_with_auth, handing rows to sink as each fetch window completes instead of assembling them, so peak memory is one window of partitions. The returned CompletedStatement keeps the metadata; its rows are empty because every row went to the sink.