[Bug] SET_VAR in a single sql affects the Session value

[Userwhite]

Describe the bug
/*+ SET_VAR(..) */ has changed the session value.
All sql are affected in the same session.

To Reproduce
1、sql: select/+ query_timeout = 0/ 1 + 2;
2、sql: select 1 + 2;
3、sql: select/+ query_timeout = 10/ 1 + 2;
4、sql: select 1 + 2;

Expected behavior
the second sql and the fourth sql should be the same result;
But the second sql is timeout,and the fourth sql is correct.