cmds系统数据库源端大表数据更新优化

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

           /

```