Script:partition table into rowid extent chunks

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
           /

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