优化Oracle 11g runstats脚本对比分析

Runstats.sql
This is the test harness I use to try out different ideas. It shows two vital sets of statistics for me 
The elapsed time difference between two approaches. It very simply shows me which approach is faster by the wall clock 
How many resources each approach takes. This can be more meaningful then even the wall clock timings. For example, if one approach is faster then the other but it takes thousands of latches (locks), I might avoid it simply because it will not scale as well. 
The way this test harness works is by saving the system statistics and latch information into a temporary table. We then run a test and take another snapshot. We run the second test and take yet another snapshot. Now we can show the amount of resources used by approach 1 and approach 2. 
Requirements 

In order to run this test harness you must at a minimum have: 

Access to V$STATNAME, V$MYSTAT, v$TIMER and V$LATCH 
You must be granted select DIRECTLY on SYS.V_$STATNAME, SYS.V_$MYSTAT, SYS.V_$TIMER and SYS.V_$LATCH. It will not work to have select on these via a ROLE. 
The ability to create a table -- run_stats -- to hold the before, during and after information. 
The ability to create a package -- rs_pkg -- the statistics collection/reporting piece 
You should note also that the LATCH information is collected on a SYSTEM WIDE basis. If you run this on a multi-user system, the latch information may be technically "incorrect" as you will count the latching information for other sessions - not just your session. This test harness works best in a simple, controlled test environment. 

The table we need is very simple: 
---------------------------------------------------------------
create global temporary table run_stats
( runid varchar2(15),
  name varchar2(80),
  value int )
on commit preserve rows;
-----------------------------------------------------------------
then you can create this view:
------------------------------------------------------------------ 
create or replace view stats
as select 'STAT...' || a.name name, b.value
      from v$statname a, v$mystat b
     where a.statistic# = b.statistic#
    union all