cmds系统数据库源端大表数据更新优化
以下脚本可以用于将表按照rowid范围分区，获得指定数目的rowid Extent区间(Group sets of rows in the table into smaller chunks)， 以便于非分区表利用rowid来实现并行删除或更新
```
REM rowid_ranges should be at least 21
REM utilize this script help delete large table
REM if update large table Why not online redefinition or CTAS
-- This script spits desired number of rowid ranges to be used for any parallel operations.
-- Best to use it for copying a huge table with out of row lob columns in it or CTAS/copy the data over db links.
-- This can also be used to simulate parallel insert/update/delete operations.
-- Maximum number of rowid ranges you can get here is 255.
-- Doesn't work for partitioned tables, but with minor changes it can be adopted easily.
-- Doesn't display any output if the total table blocks are less than rowid ranges times 128.
-- It can split a table into more ranges than the number of extents
From Saibabu Devabhaktuni http://sai-oracle.blogspot.com/2006/03/how-to-split-table-into-rowid-ranges.html
set verify off
undefine rowid_ranges
undefine segment_name
undefine owner
set head off
set pages 0
set trimspool on
select 'where rowid between ''' ||sys.dbms_rowid.rowid_create(1, d.oid, c.fid1, c.bid1, 0) ||''' and ''' ||sys.dbms_rowid.rowid_create(1, d.oid, c.fid2, c.bid2, 9999) || '''' ||';'
from (select distinct b.rn,
first_value(a.fid) over(partition by b.rn order by a.fid, a.bid rows between unbounded preceding and unbounded following) fid1,
last_value(a.fid) over(partition by b.rn order by a.fid, a.bid rows between unbounded preceding and unbounded following) fid2,
first_value(decode(sign(range2 - range1),
1,
a.bid +
((b.rn - a.range1) * a.chunks1),
a.bid)) over(partition by b.rn order by a.fid, a.bid rows between unbounded preceding and unbounded following) bid1,
last_value(decode(sign(range2 - range1),
1,
a.bid +
((b.rn - a.range1 + 1) * a.chunks1) - 1,
(a.bid + a.blocks - 1))) over(partition by b.rn order by a.fid, a.bid rows between unbounded preceding and unbounded following) bid2
from (select fid,
bid,
blocks,
chunks1,
trunc((sum2 - blocks + 1 - 0.1) / chunks1) range1,
trunc((sum2 - 0.1) / chunks1) range2
from (select /*+ rule */
relative_fno fid,
block_id bid,
blocks,
sum(blocks) over() sum1,
trunc((sum(blocks) over()) / &&rowid_ranges) chunks1,
sum(blocks) over(order by relative_fno, block_id) sum2
from dba_extents
where segment_name = upper('&&segment_name')
and owner = upper('&&owner'))
where sum1 > &&rowid_ranges) a,
(select rownum - 1 rn
from dual
connect by level <= &&rowid_ranges) b
where b.rn between a.range1 and a.range2) c,
(select max(data_object_id) oid
from dba_objects
where object_name = upper('&&segment_name')
and owner = upper('&&owner')
and data_object_id is not null) d
/
```