when the runtime filter target to a constant, the PushDownContext.finalTarget is null. in this case, do not pushdown runtime filter. example: select * from (select 1 as x from T1) T2 join T3 on T2.x=T3.x when push down RF(T3.x->T2.x) inside "select 1 as x from T1", the column x is a constant, and the pushDown stopped. (cherry picked from commit 7f06cf0a0125d84c41e1edbb71366e293f70239d)