两个超大表做关联更新的优化 之 批量更新

http://blog.itpub.net/16628454/viewspace-1043225/

两个超大表做关联更新的优化
2010-12-17 13:43:01

分类： Oracle

今天同事给了两个SQL，超级大，一个表8000多万，一个表7800万，原语句如下：

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update CHANNEL_CHENGDU.o_user_CONS partition(p201011) A

SET unuser_flag = (SELECT unuser_flag

FROM CHANNEL_CHENGDU.o_user partition(p201011) B

WHERE A.SERV_ID = B.SERV_ID)

where EXISTS (SELECT 1

FROM CHANNEL_CHENGDU.o_user partition(p201011) B

WHERE A.SERV_ID = B.SERV_ID);

update CHANNEL_CHENGDU.o_user_CONS partition(p201011) A

SET BILL_USER_FLAG = (SELECT BILL_USER_FLAG

FROM CHANNEL_CHENGDU.o_user partition(p201011) B

WHERE A.SERV_ID = B.SERV_ID)

where EXISTS (SELECT 1

FROM CHANNEL_CHENGDU.o_user partition(p201011) B

WHERE A.SERV_ID = B.SERV_ID);

这两条语句在执行第一条的时候执行了6个小时没出结果，就被杀掉了，光回滚就用了2个小时，当时开发人员急于要结果，于是我用以前看到的一篇帖子中提到的方法（http://www.itpub.net/thread-1052077-1-7.html）来解决，其实还是bulk connect，第一条语句跑了899秒，第二条跑了708秒。经过开发人员的逻辑验证，结果是正确的，但我始终对业务逻辑产生怀疑，不过这是后话，毕竟自己对应用不了解，好吧，看下改后的语句。

-----执行了889秒

declare

maxrows number default 5000;

row_id_table dbms_sql.Urowid_Table;

p_id_table dbms_sql.Number_Table;

cursor acnt_first_cur is

SELECT /* use_hash(A,B) parallel(A 4) parallel(B 4) */

b.unuser_flag, b.rowid row_id

FROM CHANNEL_CHENGDU.o_user partition(p201011) B,

CHANNEL_CHENGDU.o_user_CONS partition(p201011) A

WHERE A.SERV_ID = B.SERV_ID

and EXISTS (SELECT /*+use_hash(C,D) parallel(C 4) parallel(D 4)*/

1

FROM CHANNEL_CHENGDU.o_user partition(p201011) C,

CHANNEL_CHENGDU.o_user_CONS partition(p201011) D

WHERE C.SERV_ID = D.SERV_ID)

order by b.rowid;

begin

open acnt_first_cur;

loop

exit when acnt_first_cur%notfound;

fetch acnt_first_cur bulk collect

into p_id_table, row_id_table limit maxrows;

forall i in 1 .. row_id_table.count

update CHANNEL_CHENGDU.o_user_CONS partition(p201011)

set unuser_flag = p_id_table(i)

where rowid = row_id_table(i);

commit;

end loop;

end;

/

-----708秒

declare

maxrows number default 5000;

row_id_table dbms_sql.Urowid_Table;

p_id_table dbms_sql.Number_Table;

cursor acnt_first_cur is

SELECT /* use_hash(A,B) parallel(A 4) parallel(B 4) */

b.BILL_USER_FLAG, b.rowid row_id

FROM CHANNEL_CHENGDU.o_user partition(p201011) B,

CHANNEL_CHENGDU.o_user_CONS partition(p201011) A

WHERE A.SERV_ID = B.SERV_ID

and EXISTS (SELECT /*+use_hash(C,D) parallel(C 4) parallel(D 4)*/

1

FROM CHANNEL_CHENGDU.o_user partition(p201011) C,

CHANNEL_CHENGDU.o_user_CONS partition(p201011) D

WHERE C.SERV_ID = D.SERV_ID)

order by b.rowid;

begin

open acnt_first_cur;

loop

exit when acnt_first_cur%notfound;

fetch acnt_first_cur bulk collect

into p_id_table, row_id_table limit maxrows;

forall i in 1 .. row_id_table.count

update CHANNEL_CHENGDU.o_user_CONS partition(p201011)

set BILL_USER_FLAG = p_id_table(i)

where rowid = row_id_table(i);

commit;

end loop;

end;

/