的Oracle SQL - 查询时间限制

Question

以类似的方式来

select * from mytable where rownum <= 1000; 

将如何给我的第1000行的查询结果的，是有办法

select * from mytable where runtime <= 1000; 

这将返回运行查询的第一个1000 <时间单元中获得的结果？

Answer 1

Oracle does not support this，至少不像你的例子那样容易理解。

One blog我发现能够限制用户在他们所做的某个资源组中的执行时间。他们为所述用户创建了一个特殊组，然后他们为该用户定义了他们称为LIMIT_EXEC_TIME的资源计划。他们的代码参考如下：

set serverout on size 5555 
-- 
-- first remove an existing active plan 
ALTER SYSTEM SET RESOURCE_MANAGER_PLAN =''; 
-- 
-- delete any existing plan or group 
-- we have to create a pending area first 
exec dbms_resource_manager.clear_pending_area(); 
exec dbms_resource_manager.create_pending_area(); 
exec dbms_resource_manager.DELETE_PLAN ('LIMIT_EXEC_TIME'); 
exec dbms_resource_manager.DELETE_CONSUMER_GROUP ('GROUP_WITH_LIMITED_EXEC_TIME'); 
exec DBMS_RESOURCE_MANAGER.VALIDATE_PENDING_AREA; 

exec DBMS_RESOURCE_MANAGER.SUBMIT_PENDING_AREA(); 
begin 
    dbms_resource_manager.create_pending_area(); 
    -- 
    -- we need a consumer group that maps to the desired oracle user: 
    dbms_resource_manager.create_consumer_group(
    CONSUMER_GROUP=>'GROUP_WITH_LIMITED_EXEC_TIME', 
    COMMENT=>'This is the consumer group that has limited execution time per statement' 
    ); 
    dbms_resource_manager.set_consumer_group_mapping(
    attribute => DBMS_RESOURCE_MANAGER.ORACLE_USER, 
    value => 'PYTHIAN', 
    consumer_group =>'GROUP_WITH_LIMITED_EXEC_TIME' 
); 

    -- and we need a resource plan: 
    dbms_resource_manager.create_plan(
    PLAN=> 'LIMIT_EXEC_TIME', 
    COMMENT=>'Kill statement after exceeding total execution time' 
); 

    -- now let's create a plan directive for that special user group 
    -- the plan will cancel the current SQL if it runs for more than 120 sec 
    dbms_resource_manager.create_plan_directive(
    PLAN=> 'LIMIT_EXEC_TIME', 
    GROUP_OR_SUBPLAN=>'GROUP_WITH_LIMITED_EXEC_TIME', 
    COMMENT=>'Kill statement after exceeding total execution time', 
    SWITCH_GROUP=>'CANCEL_SQL', 
    SWITCH_TIME=>15, 
    SWITCH_ESTIMATE=>false 
); 

    dbms_resource_manager.create_plan_directive(
    PLAN=> 'LIMIT_EXEC_TIME', 
    GROUP_OR_SUBPLAN=>'OTHER_GROUPS', 
    COMMENT=>'leave others alone', 
    CPU_P1=>100 
); 

    DBMS_RESOURCE_MANAGER.VALIDATE_PENDING_AREA; 

    DBMS_RESOURCE_MANAGER.SUBMIT_PENDING_AREA(); 

end; 
/

exec dbms_resource_manager_privs.grant_switch_consumer_group('PYTHIAN','GROUP_WITH_LIMITED_EXEC_TIME',false); 

exec dbms_resource_manager.set_initial_consumer_group('PYTHIAN','GROUP_WITH_LIMITED_EXEC_TIME'); 

select * from DBA_RSRC_CONSUMER_GROUPS; 
select * from DBA_RSRC_GROUP_MAPPINGS; 
select * from DBA_RSRC_PLANS; 
select * from DBA_RSRC_PLAN_DIRECTIVES; 

-- to enable it: 
ALTER SYSTEM SET RESOURCE_MANAGER_PLAN ='LIMIT_EXEC_TIME'; 

SELECT se.sid sess_id, co.name consumer_group, 
se.state, se.consumed_cpu_time cpu_time, se.cpu_wait_time, se.queued_time 
FROM v$rsrc_session_info se, v$rsrc_consumer_group co 
WHERE se.current_consumer_group_id = co.id; 

select username,resource_CONSUMER_GROUP,count(*) from v$session group by username,resource_CONSUMER_GROUP; 

部分结果

查询可以返回部分结果，但查询也将抛出异常“ORA-00040：活动时间超出限制 - 呼叫中止”，但必须被客户忽略。

create or replace function sleep_cpu return number authid current_user is 
    v_loop number := 0; 
begin 
    for i in 1 .. 10000000 loop 
     v_loop := v_loop + 1; 
    end loop; 

    return v_loop; 
end; 
/

SQL * Plus能够证明能够阅读部分结果客户端：

SQL> set timing on 
SQL> select sleep_cpu() 
    2 from dual 
    3 connect by level <= 100; 

SLEEP_CPU() 
----------- 
    10000000 
    10000000 
    10000000 
    10000000 
    10000000 
    10000000 
    10000000 
    10000000 
    10000000 
    10000000 
    10000000 
    10000000 
    10000000 
    10000000 
    10000000 
ERROR: 
ORA-00040: active time limit exceeded - call aborted 


15 rows selected. 

Elapsed: 00:00:08.52 
SQL> 

注意经过的时间

这可以用做了很多CPU工作的功能来模拟在这个例子中是8秒。我将超时设置为5秒，这表明很难获得良好的精度。

CPU时间，不经过时间的

资源管理器只计算CPU时间，不经过时间。尽管文档说明了这一点。 Pythian文章中的一条评论表明，这种行为可以通过ALTER SYSTEM SET EVENT = '10720 trace name context forever, level 16384' scope=spfile;（以及重新启动）进行更改，但这对我无效。因为它不使用CPU 100秒

create or replace function sleep_no_cpu return number authid current_user is 
begin 
    execute immediate 'begin dbms_lock.sleep(1); end;'; 
    return 1; 
end; 
/

这个SELECT将整个百秒运行：

例如，创建此功能。

select sleep_cpu() 
from dual 
connect by level <= 100;