[DA/튜닝] oracle cluster_by_rowid

// cluster_by_rowid 

// clustering factor 가 낮을 때 사용하면 빠른 결과 도출

select /*+ ordered use_nl(b) rowid(b) */ b.*
from  (select /*+ index(emp emp_X1) no_merge */ 
              rowid rid 
       from   emp 
       where  ename = 'SCOTT'
       order by rowid) a, emp b
where  b.rowid = a.rid ;


-- after 12c
select /*+ cluster_by_rowid(e) index(e emp_x1) */ * 
from   emp e 
where  ename = 'SCOTT' ;