>For the same query by sql pass-through, when I use asynchronous mode, I got the result in 80 seconds, and synchronous mode in less than 5 seconds. How to explain that's so longer by asynchronous mode?

because the backend must execute the whole select, it store the result into a temporary table.
When the client read the data,
the backend has to pick them up from the temporary table.
This require an overhead.