当参数相同时从运行锁定过程，但当参数不同时允许

Question

如何在参数相同时阻止过程运行ning 并在参数不同时允许。让我解释一下确切的问题

正在创建构建脚本

drop table datalock_test;
create table datalock_test
(year_ number) tablespace wad;
drop TYPE test_lock_type_arr;
drop TYPE test_lock_type;
create or replace TYPE test_lock_type AS OBJECT
                   (
                    year_ number
                    );
/                    
create or replace TYPE test_lock_type_arr IS TABLE OF test_lock_type
;
/
drop procedure insert_to_lock_test;
create or replace procedure insert_to_lock_test (p_year number)
as 
    l_arr test_lock_type_arr := test_lock_type_arr();
begin
select test_lock_type(year_) bulk collect into l_arr from (select p_year as year_ from dual) a
where not exists (select NULL from  datalock_test  b
where a.year_ = b.year_);
dbms_lock.sleep(15);
forall i IN l_arr.first .. l_arr.last SAVE EXCEPTIONS
insert  into datalock_test
values
(
l_arr(i).year_
);

commit;
end;
/
truncate table datalock_test;

正常测试：-

现在如果我运行下面的代码将插入一条记录

begin
insert_to_lock_test(p_year => 1999);
end;
/

现在，如果我再次运行上面的代码，将不会插入任何记录。

硬测试：-

但是如果我在下面运行那么重复的记录将被插入，这是不可取的。

begin
dbms_scheduler.create_job (
job_name => 'load1',
job_type => 'plsql_block',
job_action => 'begin
insert_to_lock_test(p_year => 2000);
end;',
enabled => true);
dbms_scheduler.create_job (
job_name => 'load2',
job_type => 'plsql_block',
job_action => 'begin
insert_to_lock_test(p_year => 2000);
end;',
enabled => true);
end;
/

这种重复是我必须避免的。

约束：-

我无法创建唯一索引或主键。
我不能使用任何额外的检查和存在条件。

我尝试过的：-

已尝试独占锁。但这里的问题是它也阻止了以下功能。在下面的情况下，参数不同，因此进程应该能够并行运行。让我提供有关如何完成此操作的代码

重新创建程序如下

create or replace procedure insert_to_lock_test (p_year number)
as 
    l_arr test_lock_type_arr := test_lock_type_arr();
    lv_lockhandle VARCHAR2(500);
    lv_ret_code   PLS_INTEGER;
    lv_retcode    NUMBER;
    p_nm varchar2(200) := 'testlock';
begin
dbms_lock.allocate_unique(p_nm, lv_lockhandle);
    lv_retcode := dbms_lock.request(lockhandle=>lv_lockhandle, 
                                 lockmode => dbms_lock.x_mode);
select test_lock_type(year_) bulk collect into l_arr from (select p_year as year_ from dual) a
where not exists (select NULL from  datalock_test  b
where a.year_ = b.year_);
dbms_lock.sleep(15);
forall i IN l_arr.first .. l_arr.last SAVE EXCEPTIONS
insert  into datalock_test
values
(
l_arr(i).year_
);

commit;
lv_ret_code := dbms_lock.release(lv_lockhandle);
end;
/

Post 这让运行代码与相同的参数并行

begin
dbms_scheduler.create_job (
job_name => 'load1',
job_type => 'plsql_block',
job_action => 'begin
insert_to_lock_test(p_year => 2000);
end;',
enabled => true);
dbms_scheduler.create_job (
job_name => 'load2',
job_type => 'plsql_block',
job_action => 'begin
insert_to_lock_test(p_year => 2000);
end;',
enabled => true);
end;
/

没有插入重复项，只有一条记录，这是可取的。但现在的问题是当我们运行下面的代码

begin
dbms_scheduler.create_job (
job_name => 'load1',
job_type => 'plsql_block',
job_action => 'begin
insert_to_lock_test(p_year => 2020);
end;',
enabled => true);
dbms_scheduler.create_job (
job_name => 'load2',
job_type => 'plsql_block',
job_action => 'begin
insert_to_lock_test(p_year => 2021);
end;',
enabled => true);
end;
/

此处插入2021耗时过长，参数不同时延迟不可取

Answer 1

你的问题出在参数设置上timeout => 0

documentation 说

Number of seconds to continue trying to grant the lock. If the lock cannot be granted within this time period, then the call returns a value of 1 (timeout).

在零秒内你可能会或可能不会超时，所以有时你没有被阻止，有时你是。

删除timout参数（并使用默认MAXWAIT）或将其设置为一些实际值和检查响应值 - 如果是 1 你有超时并且必须处理它。您必须处理所有 returns != 0.

我一般 你应该经常检查 request 中的 return 代码，最好还部署一些逻辑来检测挂起的句柄并释放它们（例如设置 release_on_commit)

例子

注意位更新过程。尽管删除了 timeout 参数，但我检查了 request 函数的 return 代码。

最后我添加了 p_wait 参数，这样我就可以安排 blocking 过程和 testing没有等待的程序，我可以清楚地看到行为，这也记录在程序的总运行时间中。

一切正常 - 见下文

create or replace procedure testlockProc (p_nm varchar2, p_wait int default 0)
as
lv_lockhandle VARCHAR2(500);
    lv_ret_code   PLS_INTEGER;
    lv_retcode    NUMBER;
    request_failed EXCEPTION;
    lv_start DATE;
begin
    lv_start := sysdate;
    dbms_lock.allocate_unique(p_nm, lv_lockhandle);
    DBMS_OUTPUT.PUT_LINE (' got handle '|| lv_lockhandle);
    lv_retcode := dbms_lock.request(lockhandle=>lv_lockhandle, /**timeout => 0,**/
                                 lockmode => dbms_lock.x_mode);
    if lv_retcode != 0 then
       raise request_failed;
    end if;
    DBMS_OUTPUT.PUT_LINE ('request got REGEST response '|| lv_retcode);                                
    dbms_lock.sleep(p_wait);
    lv_ret_code := dbms_lock.release(lv_lockhandle);
    DBMS_OUTPUT.PUT_LINE ('release got REGEST response '|| lv_retcode|| ' in ' || to_char( round((sysdate-lv_start)*24*3600))|| ' seconds');   
end;
/

-- session 1 - procedure blocks the parameter for 60 seconds
set serveroutput on
begin
testlockProc (p_nm => 'wow', p_wait => 60);
end;
/

got handle 1073741964107374196448
request got REGEST response 0
release got REGEST response 0 in 60 seconds


-- session 2  (procedure blocked due to identical parameter from session 1)

set serveroutput on
begin
testlockProc (p_nm => 'wow');
end;
/

got handle 1073741964107374196448
request got REGEST response 0
release got REGEST response 0 in 50 seconds

-- session 3 different parameter (handle) - runns immediately

set serveroutput on
begin
testlockProc (p_nm => 'wow23');
end;
/

got handle 1073741965107374196549
request got REGEST response 0
release got REGEST response 0 in 0 seconds

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