select dealid,
       orderseqid,
       dealamount,
       dealstatus,
       dealcode,
       d.payeefee,
       d.payerfee,
       d.transactiondate,
       sysdate
  from david.test1 d
 where exists (select /*+ index_ffs(tfp) parallel_index(tfp 3)*/
         0
          from david.test2 tfp
         where d.orderseqid = tfp.sequenceid);

原因很简单，因为内部索引是INDEX FAST FULL SCAN，索引必须先指定正确的索引扫描方式，然后并行扫描索引部分的hint才能生效