如何给Large Delete操作提速近千倍?(六)

王朝厨房·作者佚名  2007-01-04
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摘要:如何给Large Delete操作提速近千倍?(六)

本文已经发表在ITPUB优化技术丛书,未经许可,不得转载。

本文已经发表在ITPUB优化技术丛书,未经许可,不得转载。

1.1. 第五次优化——使用FORALL + 原子级操作

这一次的优化过程已经很清晰了,主要是综合了前面几次优化的思想,将他们的优点集中使用,即:

1) 分段处理:将整个大的事务分割为以10000行为单位的小事务,其中,10000这个基数来自于上面使用批量测试时的结果(从删除10000条记录到删除100000条记录,所需要的操作时间已经出现了比较大的倍数关系)。

2) 拆分操作:避开庞大的IN-LIST条件,而是采用原子级的处理。

3) 批量绑定:使用FORALL进行批量绑定,以数组方式处理,大大减少了PL/SQL引擎和SQL引擎的上下文切换,从而提高了处理速度。

现在,首先来构造以10000为单位的FORALL处理过程:

create or replace procedure del_hubei_SSF_forall

as

type ridArray is table of rowid index by binary_integer;

type dtArray is table of varchar2(50) index by binary_integer;

v_rowid ridArray;

v_mid_to_delete dtArray;

begin

select mid,rowid bulk collect into v_mid_to_delete,v_rowid from temp_mid_hubei_bak where rownum<10001;

forall i in 1 .. v_mid_to_delete.COUNT

delete from SSF where mid = v_mid_to_delete(i);

-- DBMS_OUTPUT.PUT_LINE(to_char(v_mid_to_delete.COUNT)||’ records deleted from hubei_SSF !!!’);

forall i in 1 .. v_rowid.COUNT

delete from temp_mid_hubei_bak where rowid = v_rowid(i);

-- DBMS_OUTPUT.PUT_LINE(to_char(v_rowid.COUNT)||’ records deleted from temp_mid_hubei_bak !!!’);

end;

/

然后构造始终按照10000条循环批量删除的过程:

create or replace procedure exec_forall

(

p_RowCount in number, -- Total need to delete rows count

p_ExeCount in number -- Every times need to delete rows count

)

as

n_RowCount number:=0; -- Yet needed to delete rows count

n_ExeTimes number:=0; -- execute times(loop times)

n_delete number:=0; -- really delete rows count

begin

n_RowCount := p_RowCount;

while n_RowCount >0 loop

EXECUTE IMMEDIATE ’begin del_hubei_SUBSREGINFO_forall; end;’;

commit;

if n_RowCount>p_ExeCount then

n_RowCount:= n_RowCount-p_ExeCount;

n_ExeTimes := n_ExeTimes + 1;

else

n_ExeTimes := n_ExeTimes + 1;

n_delete := n_RowCount;

n_RowCount:= n_RowCount-p_ExeCount;

end if;

DBMS_OUTPUT.PUT_LINE(’---------’||to_char(n_ExeTimes)||’-----------’);

n_delete := n_delete+p_ExeCount*(n_ExeTimes-1);

end loop;

DBMS_OUTPUT.PUT_LINE(’Full Finished!!!’);

DBMS_OUTPUT.PUT_LINE(’Totally ’||to_char(n_delete)||’ records deleted. !!!’);

end;

/

好了,现在来测试一下,这次优化的成果吧:

首先,看一下临时表的记录数目:

SQL> select count(*) temp_mid_hubei from temp_mid_hubei_bak;

TEMP_MID_HUBEI

--------------

1444661

Elapsed: 00:00:02.41

SQL>

再检查一下业务大表的记录数目;

SQL> SELECT COUNT(*) SSF FROM SSF;

SSF

-----------

83446270

ELAPSED: 00:04:53.27

SQL>

首先,我们删除500000行记录,看看需要多少时间完成:

SQL> exec exec_forall(500010,10001);

10000 records deleted from hubei_SSF !!!

10000 records deleted from temp_mid_hubei_bak !!!

---------1-----------

10000 records deleted from hubei_SSF !!!

10000 records deleted from temp_mid_hubei_bak !!!

---------2-----------

10000 records deleted from hubei_SSF !!!

10000 records deleted from temp_mid_hubei_bak !!!

---------3-----------

10000 records deleted from hubei_SSF !!!

10000 records deleted from temp_mid_hubei_bak !!!

---------4-----------

10000 records deleted from hubei_SSF !!!

10000 records deleted from temp_mid_hubei_bak !!!

---------5-----------

10000 records deleted from hubei_SSF !!!

10000 records deleted from temp_mid_hubei_bak !!!

---------6-----------

。。。。。。。。。。。(这里省略掉了一些雷同的输入)

---------50-----------

Full Finished!!!

Totally 500010 records deleted. !!!

PL/SQL procedure successfully completed.

Elapsed: 00:02:57.78

SQL>

这是个惊人的数字,2分57秒!!

于是再来删除90万试试看:

SQL> exec exec_forall(900010,10001);

10000 records deleted from hubei_SSF !!!

10000 records deleted from temp_mid_hubei_bak !!!

---------1-----------

10000 records deleted from hubei_SSF !!!

10000 records deleted from temp_mid_hubei_bak !!!

---------2-----------

10000 records deleted from hubei_SSF !!!

10000 records deleted from temp_mid_hubei_bak !!!

---------3-----------

10000 records deleted from hubei_SSF !!!

10000 records deleted from temp_mid_hubei_bak !!!

---------4-----------

10000 records deleted from hubei_SSF !!!

10000 records deleted from temp_mid_hubei_bak !!!

---------5-----------

10000 records deleted from hubei_SSF !!!

10000 records deleted from temp_mid_hubei_bak !!!

---------6-----------

。。。。。。。。。

---------86-----------

10000 records deleted from hubei_SSF !!!

10000 records deleted from temp_mid_hubei_bak !!!

---------87-----------

10000 records deleted from hubei_SSF !!!

10000 records deleted from temp_mid_hubei_bak !!!

---------88-----------

10000 records deleted from hubei_SSF !!!

10000 records deleted from temp_mid_hubei_bak !!!

---------89-----------

10000 records deleted from hubei_SSF !!!

10000 records deleted from temp_mid_hubei_bak !!!

---------90-----------

Full Finished!!!

Totally 900010 records deleted. !!!

PL/SQL procedure successfully completed.

Elapsed: 00:02:33.47

SQL>

SQL> select count(*) temp_mid_hubei from temp_mid_hubei_bak;

TEMP_MID_HUBEI

--------------

34661

Elapsed: 00:00:00.46

SQL>

删除90万的数据只需要2分33秒!!和删除50万数据量相比,使用的操作时间差不多。

到此,此次任务已经可以圆满完成了(将所有的操作使用这种优化思想写成脚本,很快就可以完成任务)。

 
 
 
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