(很抱歉这篇文章很长,但我想所有信息都是非常必要的)
我们有两个表 - 任务和子任务。每个任务由一个或多个子任务组成,每个对象都有开始日期、结束日期和持续时间。此外,子任务有顺序。
Tables
create table task (
pk number not null primary key,
name varchar2(30) not null,
start_date date,
duration_in_days number,
end_date date,
needs_recomputation number default 0
);
create table subtask (
pk number not null primary key,
task_fk references task(pk),
name varchar2(30) not null,
start_date date,
duration_in_days number,
end_date date,
ordering number not null
);
商业规则
- 第一个子任务与任务具有相同的开始日期
- 对于每个后续子任务,其开始日期等于前一个子任务的结束日期
- 最后一个子任务与任务具有相同的结束日期
- 对于每个子任务和任务:
start_date + duration = end_date
- 对于任务:
duration = sum(duration of subtasks)
- 任务的结束日期和持续时间不能直接更改(感谢上帝!)
这直接生成以下更新/删除的要求:
- 当任务的开始日期更改时,其第一个子任务的开始日期将设置为相同的值,并重新计算所有子任务的开始日期和结束日期
- 当子任务的开始日期、结束日期或持续时间更改时,其他字段会相应更新,所有后续子任务也会相应更新,最后任务也会相应更新
- 当删除一个子任务时,所有后续子任务都会相应更新,最后该任务也会相应更新
目前的方法
- 任务表有一个触发器,用于更新第一个子任务并在开始日期更改时设置 need_recomputation 标志
- 子任务表有一个触发器,可以保持开始日期/结束日期/持续时间一致,并为父任务设置needs_recomputation标志(由于变异表问题,我们无法直接更新此处的后续任务)
- 为了避免触发器级联,每个触发器都会设置一个包变量来指示不应触发其他触发器
- dbms_scheduler 作业定期检查任务表并重新计算设置了 need_recomputation 标志的任务的数据
这(有点)有效,但有几个缺点:
- 如果几个人同时更改同一任务的数据,我们可能会得到不一致的数据(请参阅向 Tom 询问触发器问题 http://www.oracle.com/technetwork/issue-archive/2008/08-sep/o58asktom-101055.html)
- 子任务表更新后,我们会在很短的时间内出现数据不一致的情况(直到下次同步作业运行为止)。目前,我们在 GUI 中每次更改操作后手动运行作业,但这显然容易出错
所以我的问题是 - 是否有任何明智的替代方法?
Package
create or replace package pkg_task is
g_update_in_progress boolean;
procedure recomputeDates(p_TaskID in task.pk%TYPE);
procedure recomputeAllDates;
end;
create or replace package body pkg_task is
procedure recomputeDates(p_TaskID in task.pk%TYPE) is
begin
g_update_in_progress := true;
-- update the subtasks
merge into subtask tgt
using (select pk,
start_date,
duration_in_days,
end_date,
sum(duration_in_days) over(partition by task_fk order by ordering) as cumulative_duration,
min(start_date) over(partition by task_fk) + sum(duration_in_days) over(partition by task_fk order by ordering rows between unbounded preceding and 1 preceding) as new_start_date,
min(start_date) over(partition by task_fk) + sum(duration_in_days) over(partition by task_fk order by ordering) as new_end_date
from subtask s
where s.task_fk = p_TaskID
order by task_fk,
ordering) src
on (src.pk = tgt.pk)
when matched then
update
set tgt.start_date = nvl(src.new_start_date,
src.start_date),
tgt.end_date = nvl(src.new_end_date,
src.end_date);
-- update the task
merge into task tgt
using (select p_TaskID as pk,
min(s.start_date) as new_start_date,
max(s.end_date) as new_end_date,
sum(s.duration_in_days) as new_duration
from subtask s
where s.task_fk = p_TaskID) src
on (tgt.pk = src.pk)
when matched then
update
set tgt.start_date = src.new_start_date,
tgt.end_date = src.new_end_date,
tgt.duration_in_days = src.new_duration,
tgt.needs_recomputation = 0;
g_update_in_progress := false;
end;
procedure recomputeAllDates is
begin
for cur in (select pk
from task t
where t.needs_recomputation = 1)
loop
recomputeDates(cur.pk);
end loop;
end;
begin
g_update_in_progress := false;
end;
Triggers
create or replace trigger trg_task
before update on task
for each row
begin
if (:new.start_date <> :old.start_date and not pkg_task.g_update_in_progress) then
pkg_task.g_update_in_progress := true;
-- set the start date for the first subtask
update subtask s
set s.start_date = :new.start_date
where s.task_fk = :new.pk
and s.ordering = 1;
:new.needs_recomputation := 1;
pkg_task.g_update_in_progress := false;
end if;
end;
create or replace trigger trg_subtask
before update on subtask
for each row
declare
l_date_changed boolean := false;
begin
if (not pkg_task.g_update_in_progress) then
pkg_task.g_update_in_progress := true;
if (:new.start_date <> :old.start_date) then
:new.end_date := :new.start_date + :new.duration_in_days;
l_date_changed := true;
end if;
if (:new.end_date <> :old.end_date) then
:new.duration_in_days := :new.end_date - :new.start_date;
l_date_changed := true;
end if;
if (:new.duration_in_days <> :old.duration_in_days) then
:new.end_date := :new.start_date + :new.duration_in_days;
l_date_changed := true;
end if;
if l_date_changed then
-- set the needs_recomputation flag for the parent task
-- if this is the first subtask, set the parent's start date, as well
update task t
set t.start_date =
(case
when :new.ordering = 1 then
:new.start_date
else
t.start_date
end),
t.needs_recomputation = 1
where t.pk = :new.task_fk;
end if;
pkg_task.g_update_in_progress := false;
end if;
end;
Job
begin
dbms_scheduler.create_job(
job_name => 'JOB_SYNC_TASKS'
,job_type => 'PLSQL_BLOCK'
,job_action => 'begin pkg_task.recomputeAllDates; commit; end; '
,start_date => to_timestamp_tz('2014-01-14 10:00:00 Europe/Berlin',
'yyyy-mm-dd hh24:mi:ss tzr')
,repeat_interval => 'FREQ=HOURLY;BYMINUTE=0,5,10,15,20,25,30,35,40,45,50,55'
,enabled => TRUE
,comments => 'Task sync job, runs every 5 minutes');
end;