如何给Large Delete操作提速近千倍?(五)

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?(五)

1.1. 第四次优化——使用FORALL 处理批量作业

上面我们已经介绍了批量作业的一些概念,这里不再赘述。

这次优化的思想主要是使用FORALL的思路来改写“第三次优化——拆分DELETE操作”,具体的修改如下:

SQL> l

1 create or replace procedure del_hubei_SSR_forall

2 as

3 type ridArray is table of rowid index by binary_integer;

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

5

6 v_rowid ridArray;

7 v_mid_to_delete dtArray;

8

9 begin

10 select mid,rowid bulk collect into v_mid_to_delete,v_rowid from temp_mid_hubei where rownum<11;

11

12 forall i in 1 .. v_mid_to_delete.COUNT

13 delete from SSR where mid = v_mid_to_delete(i);

14

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

16 DBMS_OUTPUT.PUT_LINE(’Totally ’||to_char(v_mid_to_delete.COUNT)||’ records deleted from hubei_SSR !!!’);

17

18 forall i in 1 .. v_rowid.COUNT

19 delete from temp_mid_hubei where rowid = v_rowid(i);

20

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

22 DBMS_OUTPUT.PUT_LINE(’Totally ’||to_char(v_rowid.COUNT)||’ records deleted from temp_mid_hubei !!!’);

23

24* end;

SQL> /

Procedure created.

Elapsed: 00:00:00.07

SQL>

SQL> exec del_hubei_SSR_forall;

Full Finished!!!

Totally 10 records deleted from hubei_SSR !!!

Full Finished!!!

Totally 10 records deleted from temp_mid_hubei !!!

PL/SQL procedure successfully completed.

Elapsed: 00:00:00.16

SQL>

这里应用了上面我们说过的SELECT BULK COLLECT INTO 方法来进行批量绑定,根据以10条记录为一组的测试结果表名,速度比较理想,于是再测1000条记录的情况:

SQL> exec del_hubei_SSR_forall;

Full Finished!!!

Totally 1000 records deleted from hubei_SSR !!!

Full Finished!!!

Totally 100 records deleted from temp_mid_hubei !!!

PL/SQL procedure successfully completed.

Elapsed: 00:00:00.66

SQL>

测试结果还是比较稳定,于是再测10000和100000条记录的情况:

SQL> exec del_hubei_SSR_forall;

Full Finished!!!

Totally 10000 records deleted from hubei_SSR !!!

Full Finished!!!

Totally 10000 records deleted from temp_mid_hubei !!!

PL/SQL procedure successfully completed.

Elapsed: 00:00:04.07

SQL>

SQL> exec del_hubei_SSR_forall;

Full Finished!!!

Totally 100000 records deleted from hubei_SSR !!!

Full Finished!!!

Totally 100000 records deleted from temp_mid_hubei !!!

PL/SQL procedure successfully completed.

Elapsed: 00:03:51.29

SQL>

这里我们注意到,完成删除10000记录需要4秒中,而完成100000条记录的删除需要将近4分钟,也就是说,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。

下面再测试一下50万条记录的情况:

SQL> exec del_hubei_SSR_forall;

Full Finished!!!

Totally 509555 records deleted from hubei_SSR !!!

Full Finished!!!

Totally 509555 records deleted from temp_mid_hubei !!!

PL/SQL procedure successfully completed.

Elapsed: 00:39:04.41

SQL>

这里,删除500000条记录已经需要将近40分钟了!

到这里,基本上可以得出结论,使用批量删除虽然可以解决一定的问题,但是如果需要操作的数组太大,那么执行结果会打打折扣,这个是不难理解的。

于是,第五次优化的思路就产生了:

1) 分段处理

2) 拆分操作

3) 批量绑定

 
 
 
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