Function aggregate 

pub async fn aggregate<S: StorageEngine>(
    array_state: &Arc<Mutex<ArrayEngineState>>,
    storage: &Arc<S>,
    name: &str,
    attr_idx: u32,
    reducer: ArrayReducer,
    group_by_dim_idx: i32,
) -> Result<QueryResult, LiteError>

Execute ArrayOp::Aggregate for the Lite engine.