Query performance improvement using pipelined table function

Question

Hi,
I have got two select queries one is like...
select * from table
another is using pielined table function
select *
from table(pipelined_function(cursor(select * from table)))
which query will return result set more faster????????
suggest methods for retrieving dataset more faster (using pipelined table function) than a normal select query.
rgds
somy

Answer 1

Compare the performance between these solutions:
create table big as select * from all_objects;
First test the performance of a normal select statement:
begin
  for r in (select * from big) loop
   null;
  end loop;
end;
/Second a pipelined function:
create type rc_vars as object 
(OWNER  VARCHAR2(30)
,OBJECT_NAME     VARCHAR2(30));
create or replace type rc_vars_table as table of  rc_vars ;
create or replace
function rc_get_vars
return rc_vars_table
pipelined
as
  cursor c_aobj
         is
         select owner, object_name
         from   big;
  l_aobj c_aobj%rowtype;
begin
  for r_aobj in c_aobj loop
    pipe row(rc_vars(r_aobj.owner,r_aobj.object_name));
  end loop;
  return;
end;
/Test the performance of the pipelined function:
begin
  for r in (select * from table(rc_get_vars)) loop
   null;
  end loop;
end;
/On my system the simple select-statement is 20 times faster.
Correction: It is 10 times faster, not 20.
Message was edited by:
wateenmooiedag