fix change user user variables not update

src/sql/session/ob_basic_session_info.cpp

@@ -304,6 +304,11 @@ void ObBasicSessionInfo::clean_status()
   reset_session_changed_info();
 }
 
+void ObBasicSessionInfo::reset_user_var()
+{
+  user_var_val_map_.reuse();
+}
+
 void ObBasicSessionInfo::reset(bool skip_sys_var)
 {
   set_valid(false);

src/sql/session/ob_basic_session_info.h

@@ -396,6 +396,7 @@ public:
   virtual void destroy();
   //called before put session to freelist: unlock/set invalid
   virtual void reset(bool skip_sys_var = false);
+  void reset_user_var();
   void set_tenant_session_mgr(ObTenantSQLSessionMgr *tenant_session_mgr)
   {
     tenant_session_mgr_ = tenant_session_mgr;