Oracle 11g merge into log error及并行注意事项

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最近有一个业务使用 merge into 报主键冲突的错误。各地市将数据汇总到省，省的数据是按照局编码分区，由于不同的地市，有主键相同的数据，应该是垃圾数据。

– 初始化数据

drop table T_LIST purge;
drop table T_LIST1 purge;
CREATE TABLE T_LIST
(
ID NUMBER(7) NOT NULL PRIMARY KEY,
CITY VARCHAR2(10),
sort number
)
PARTITION BY LIST (CITY)
(
PARTITION P_BEIJING VALUES (‘BEIJING’) ,
PARTITION P_SHANGHAI VALUES (‘SHANGHAI’),
PARTITION P_GUANGZHOU VALUES (‘GUANGZHOU’)
);
insert into T_LIST values(1,’BEIJING’,11);
insert into T_LIST values(2,’SHANGHAI’,22);
insert into T_LIST values(3,’GUANGZHOU’,33);
commit;

CREATE TABLE T_LIST1
(
ID NUMBER(7) PRIMARY KEY,
CITY VARCHAR2(10),
sort number
)
PARTITION BY LIST (CITY)
(
PARTITION P_BEIJING VALUES (‘BEIJING’) ,
PARTITION P_SHANGHAI VALUES (‘SHANGHAI’),
PARTITION P_GUANGZHOU VALUES (‘GUANGZHOU’)
);
insert into T_LIST1 values(1,’BEIJING’,111);
insert into T_LIST1 values(3,’SHANGHAI’,222);
insert into T_LIST1 values(2,’GUANGZHOU’,333);
commit;
– 建立错误日志表
EXEC DBMS_ERRLOG.CREATE_ERROR_LOG(‘T_LIST’, ‘T_ERROR_LOG’);

declare
Type city is table of varchar2(10);
v_city city := city(‘BEIJING’, ‘SHANGHAI’, ‘GUANGZHOU’);
V_SQL VARCHAR2(4000) :=
‘merge into T_LIST a using(select * from T_LIST1 where CITY = :1) b
on (a.id = b.id and a.city = b.city and a.city = :2)
when matched then
update set a.sort=b.sort
when not matched then
insert values(b.id,b.city,b.sort) LOG ERRORS INTO T_ERROR_LOG REJECT LIMIT UNLIMITED’;
begin
for i in v_city.first .. v_city.last loop
execute immediate V_SQL using v_city(i),v_city(i);
end loop;
commit;
end;

SQL> select ORA_ERR_MESG$,id,city from T_ERROR_LOG;
ORA_ERR_MESG$ ID CITY
————————————————– ———- ———-
ORA-00001: 违反唯一约束条件 (TEST.SYS_C0011594) 3 SHANGHAI

ORA-00001: 违反唯一约束条件 (TEST.SYS_C0011594) 2 GUANGZHOU

当然，在数据量大的情况下要使用并行，有可能会有问题，因为并行默认是直接路径读。

alter session enable parallel dml;
declare
Type city is table of varchar2(10);
v_city city := city(‘BEIJING’, ‘SHANGHAI’, ‘GUANGZHOU’);
V_SQL VARCHAR2(4000) :=
‘merge /*+parallel(2) */ into T_LIST a using(select * from T_LIST1 where CITY = :1) b
on (a.id = b.id and a.city = b.city and a.city = :2)
when matched then
update set a.sort=b.sort
when not matched then
insert values(b.id,b.city,b.sort) LOG ERRORS INTO T_ERROR_LOG REJECT LIMIT UNLIMITED’;
begin
for i in v_city.first .. v_city.last loop
execute immediate V_SQL using v_city(i),v_city(i);
commit;
end loop;
end;
ORA-12801: 并行查询服务器 P000 中发出错误信号
ORA-00001: 违反唯一约束条件 (TEST.SYS_C0011594)
ORA-06512: 在 line 14

解决方案是：加一个 noappend 的 hint，并行也可以改为 merge /*+parallel(a) parallel(b) noappend*/ into.
declare
Type city is table of varchar2(10);
v_city city := city(‘BEIJING’, ‘SHANGHAI’, ‘GUANGZHOU’);
V_SQL VARCHAR2(4000) :=
‘merge /*+parallel(2) noappend*/ into T_LIST a using(select * from T_LIST1 where CITY = :1) b
on (a.id = b.id and a.city = b.city and a.city = :2)
when matched then
update set a.sort=b.sort
when not matched then
insert values(b.id,b.city,b.sort) LOG ERRORS INTO T_ERROR_LOG REJECT LIMIT UNLIMITED’;
begin
for i in v_city.first .. v_city.last loop
execute immediate V_SQL using v_city(i),v_city(i);
commit;
end loop;
end;