欢迎您访问程序员文章站本站旨在为大家提供分享程序员计算机编程知识!
您现在的位置是: 首页  >  IT编程

[20180814]慎用查看表压缩率脚本.txt

程序员文章站 2022-05-31 13:51:56
[20180814]慎用查看表压缩率脚本.txt--//最近看exadata方面书籍,书中提供1个脚本,查看某些表采用那些压缩模式压缩比能达到多少.--//通过调用DBMS_COMPRESSION.get_compression_ratio确定压缩比.例子如下:--//测试版本11.2.0.4.de ......

[20180814]慎用查看表压缩率脚本.txt

--//最近看exadata方面书籍,书中提供1个脚本,查看某些表采用那些压缩模式压缩比能达到多少.
--//通过调用DBMS_COMPRESSION.get_compression_ratio确定压缩比.例子如下:

--//测试版本11.2.0.4.
declare
        blockct_comp    number;
        blockct_uncomp  number;
        rows_comp       number;
        rows_uncomp     number;
        comp_rat        number;
        comp_type       varchar2(40);
begin
          dbms_compression.get_compression_ratio('&&tblspc','&&ownr','&&tblname',null,  dbms_compression.comp_for_oltp,        blockct_comp, blockct_uncomp,rows_comp,rows_uncomp, comp_rat, comp_type);
          dbms_output.put_line('Compression type: '||comp_type||'     Compression ratio (est):'||comp_rat);
          dbms_compression.get_compression_ratio('&&tblspc','&&ownr','&&tblname',null,  dbms_compression.comp_for_query_low,   blockct_comp, blockct_uncomp,rows_comp,rows_uncomp, comp_rat, comp_type);
          dbms_output.put_line('Compression type: '||comp_type||'     Compression ratio (est):'||comp_rat);
          dbms_compression.get_compression_ratio('&&tblspc','&&ownr','&&tblname',null,  dbms_compression.comp_for_query_high,  blockct_comp, blockct_uncomp,rows_comp,rows_uncomp, comp_rat, comp_type);
          dbms_output.put_line('Compression type: '||comp_type||'     Compression ratio (est):'||comp_rat);
          dbms_compression.get_compression_ratio('&&tblspc','&&ownr','&&tblname',null,  dbms_compression.comp_for_archive_low, blockct_comp, blockct_uncomp,rows_comp,rows_uncomp, comp_rat, comp_type);
          dbms_output.put_line('Compression type: '||comp_type||'     Compression ratio (est):'||comp_rat);
          dbms_compression.get_compression_ratio('&&tblspc','&&ownr','&&tblname',null,  dbms_compression.comp_for_archive_high,blockct_comp, blockct_uncomp,rows_comp,rows_uncomp, comp_rat, comp_type);
          dbms_output.put_line('Compression type: '||comp_type||'     Compression ratio (est):'||comp_rat);
end;
/

--//好奇心我想看看生产系统一张大表能达到多少.我执行上面的脚本,结果等大约2-3分钟没有结果出来,我马上中断处理.
--//我当时想既然大表可能分析数据量大,换1个点的表看看.
--//结果执行后包如下错误:

ERROR at line 1:
ORA-20000: YOU CAN NOT TRUNCATE or DROP CMP3$97116 TABLE!
ORA-06512: at line 6
ORA-06512: at "SYS.PRVT_COMPRESSION", line 1136
ORA-06512: at "SYS.PRVT_COMPRESSION", line 1114
ORA-20000: YOU CAN NOT TRUNCATE or DROP CMP1$97116 TABLE!
ORA-06512: at "SYS.DBMS_COMPRESSION", line 214
ORA-06512: at line 9

--//BTW:我们生产系统有系统触发器,禁止用户drop和truncate表.这样导致脚本运行报错.
--//我看了一下CMP3$97116,CMP1$97116表结果,和分析表结构一致.

CREATE TABLE xxxxxx_yyy.CMP4$97116
(
  ZYH        NUMBER(18)                         NOT NULL,
  ....
  YB_DBZ     VARCHAR2(4 BYTE)
)
TABLESPACE xxxxxx_yyy
RESULT_CACHE (MODE DEFAULT)
PCTUSED    0
PCTFREE    10
INITRANS   1
MAXTRANS   255
STORAGE    (
            INITIAL          64K
            NEXT             1M
            MAXSIZE          UNLIMITED
            MINEXTENTS       1
            MAXEXTENTS       UNLIMITED
            PCTINCREASE      0
            BUFFER_POOL      DEFAULT
            FLASH_CACHE      DEFAULT
            CELL_FLASH_CACHE DEFAULT
           )
NOLOGGING
COMPRESS FOR OLTP
~~~~~~~~~~~~~~~
NOCACHE
NOPARALLEL
MONITORING;

--//可以看出DBMS_COMPRESSION.get_compression_ratio操作很简单,先建立与分析表一样的表结构以及对应压缩模式的表,然后
--//导入数据后比较分析压缩比.
--//这样要耗费大量表空间与资源做这个工作,在生产系统要小心谨慎.

--//我事后认真看了<深入理解ORACLE Exadata> P98页.而是讲样本数据插入一个临时表中.同时压缩版本的临时表也被创建,比较压缩
--//版本和非压缩版本的大小就可以得到压缩率.
--//(注:我看到的不是临时表,而是真实的表,看上面的表定义.或许作者理解的临时表非我理解的临时表)
--//我不知道取样比例是多少,总之在生产系统执行该脚本还是要小心.
--//另外书P101提到 压缩助手的一大亮点是能够在非exadata平台上运行,在真正迁移数据到exadata平台之前,它能够提供足够的信息
--//帮助你做出合理的选择.这么讲非exadata平台还是能够建立hcc压缩模式的相关数据,只不过你不能查看.

--//我曾经在dg上查看压缩表信息,链接[20150727]exadata压缩HCC与dataguard.txt=>http://blog.itpub.net/267265/viewspace-1753362/
XXXX@zzzzdg2> select * from t where rownum<=1;
select * from t where rownum<=1
              *
ERROR at line 1:
ORA-64307:  Exadata Hybrid Columnar Compression is not supported for tablespaces on this storage type

--//在家里测试的结果.
SCOTT@test01p> @ ver1

PORT_STRING                    VERSION        BANNER                                                                               CON_ID
------------------------------ -------------- -------------------------------------------------------------------------------- ----------
IBMPC/WIN_NT64-9.1.0           12.1.0.1.0     Oracle Database 12c Enterprise Edition Release 12.1.0.1.0 - 64bit Production              0

create table t as select * from all_objects ;
--//反复插入,提示要大于1000000rows才可以.

SCOTT@test01p> select count(*) from t;

  COUNT(*)
----------
   1437952
--//占用192M.

Compression type: "Compress Advanced"     Compression ratio (est):3.5
Compression Advisor self-check validation successful. select count(*) on both Uncompressed and EHCC Compressed format = 1000001 rows
Compression type: "Compress Query Low"     Compression ratio (est):8.6
Compression Advisor self-check validation successful. select count(*) on both Uncompressed and EHCC Compressed format = 1000001 rows
Compression type: "Compress Query High"     Compression ratio (est):16.3
Compression Advisor self-check validation successful. select count(*) on both Uncompressed and EHCC Compressed format = 1000001 rows
Compression type: "Compress Archive Low"     Compression ratio (est):16.6
Compression Advisor self-check validation successful. select count(*) on both Uncompressed and EHCC Compressed format = 1000001 rows
Compression type: "Compress Archive High"     Compression ratio (est):21.7
PL/SQL procedure successfully completed.

--//如果单独执行如下:
--//在sys用户下建立触发器禁止drop表.

CREATE OR REPLACE TRIGGER SYS.TRI_PREVENT_DROP_TRUNCATE
   BEFORE TRUNCATE OR DROP ON DATABASE
BEGIN
   IF ora_dict_obj_type = 'TABLE' AND ora_dict_obj_owner = 'SCOTT' and ORA_DICT_OBJ_NAME not like 'SYS\_JOURNAL\_%' escape '\'
   THEN
      raise_application_error (-20000, 'YOU CAN NOT TRUNCATE or DROP ' || ora_dict_obj_name || ' TABLE!');
   END IF;
END;
/

--//如果单独执行如下:
/* Formatted on 2018/8/14 8:49:08 (QP5 v5.269.14213.34769) */
set serveroutput on
DECLARE
   blockct_comp     NUMBER;
   blockct_uncomp   NUMBER;
   rows_comp        NUMBER;
   rows_uncomp      NUMBER;
   comp_rat         NUMBER;
   comp_type        VARCHAR2 (40);
BEGIN
DBMS_COMPRESSION.get_compression_ratio
   (
      '&&tblspc'
     ,'&&ownr'
     ,'&&tblname'
     ,NULL
     ,DBMS_COMPRESSION.comp_archive_high
     ,blockct_comp
     ,blockct_uncomp
     ,rows_comp
     ,rows_uncomp
     ,comp_rat
     ,comp_type
   );
   DBMS_OUTPUT.put_line
   (
         'Compression type: '
      || comp_type
      || '     Compression ratio (est):'
      || comp_rat
   );
END;
/
--//注:12c参数DBMS_COMPRESSION.comp_archive_high与11g不同.11g写成DBMS_COMPRESSION.comp_for_archive_high
--//由于触发器建立,报错如下:
SCOTT@test01p> @ exadata/comp_radio12x.sql
old  11:       '&&tblspc'
new  11:       'USERS'
old  12:      ,'&&ownr'
new  12:      ,'SCOTT'
old  13:      ,'&&tblname'
new  13:      ,'T'
Compression Advisor self-check validation successful. select count(*) on both Uncompressed and EHCC Compressed format = 1000001 rows
DECLARE
*
ERROR at line 1:
ORA-20000: YOU CAN NOT TRUNCATE or DROP CMP1$107873 TABLE!
ORA-06512: at line 4
ORA-06512: at "SYS.PRVT_COMPRESSION", line 2134
ORA-06512: at "SYS.PRVT_COMPRESSION", line 1108
ORA-20000: YOU CAN NOT TRUNCATE or DROP CMP1$107873 TABLE!
ORA-06512: at "SYS.PRVT_COMPRESSION", line 237
ORA-06512: at "SYS.DBMS_COMPRESSION", line 215
ORA-06512: at line 9

SCOTT@test01p> select owner,object_name,CREATED from dba_objects where owner=user and object_name like 'CMP%';
OWNER                OBJECT_NAME          CREATED
-------------------- -------------------- -------------------
SCOTT                CMP4$107873          2018-08-14 20:58:05
SCOTT                CMP3$107873          2018-08-14 20:57:57
SCOTT                CMP2$107873          2018-08-14 20:57:51
SCOTT                CMP1$107873          2018-08-14 20:57:48

--//这次测试建立4张表.
SCOTT@test01p> select * from CMP4$107873;
select * from CMP4$107873
              *
ERROR at line 1:
ORA-64307:  Exadata Hybrid Columnar Compression is not supported for tablespaces on this storage type

--//可以发现oracle建立hcc表在非exadata是可行的,但是里面的数据不能看.