我有一个通常需要大约 5 分钟才能运行的 Oracle 过程。过程中有两个区域需要查询可能已被修改的 ID 号列表。这两个段中的查询是相同的。第一个在游标定义的开头，第二个在过程主体的 delete 语句中。经常重复的关键部分涉及获取刷新某个表的最新日期。整个过程相当冗长，所以我只在下面包含相关部分。
这里是光标的开头：
cursor gvg_profile_c is
with last_refreshed as
(select trunc(max(t.last_refreshed)) as max_date
from ad.pbi_gvg_profile t),
with modified_ids as
(
select distinct id_number
from ad.hr_giving cg
join ad.pbi_dates d
on d.DATE_FULL = trunc(cg.processed_date)
where d.RELATIVE_DATE >= (select max_date from last_refreshed)
and d.RELATIVE_DATE <= trunc(CURRENT_DATE)
and cg.fiscal_year >= ad.current_fiscal_year - 6
union
select distinct gi.gift_donor_id as id_number
from ad.gift gi
where gi.date_added >= (select max_date from last_refreshed)
or gi.date_modified >= (select max_date from last_refreshed)
union
select distinct p.pledge_donor_id as id_number
from ad.pledge_rev p
where p.date_added >= (select max_date from last_refreshed)
or p.date_modified >= (select max_date from last_refreshed)
union
select distinct a.id_number
from ad.affiliation a
where a.date_added >= (select max_date from last_refreshed)
or a.date_modified >= (select max_date from last_refreshed)
),
这里是删除语句：
delete from ad.pbi_gvg_profile p
where p.id_number in
(with last_refreshed as (select trunc(max(t.last_refreshed)) as max_date
from ad.pbi_gvg_profile t)
select distinct id_number
from ad.hr_giving cg
join ad.pbi_dates d
on d.DATE_FULL = trunc(cg.processed_date)
where d.RELATIVE_DATE >= (select max_date from last_refreshed)
and d.RELATIVE_DATE <= trunc(CURRENT_DATE)
and cg.fiscal_year >= ad.current_fiscal_year - 6
union
select distinct gi.gift_donor_id as id_number
from ad.gift gi
where gi.date_added >= (select max_date from last_refreshed)
or gi.date_modified >= (select max_date from last_refreshed)
union
select distinct p.pledge_donor_id as id_number
from ad.pledge_rev p
where p.date_added >= (select max_date from last_refreshed)
or p.date_modified >= (select max_date from last_refreshed)
union
select distinct a.id_number
from ad.affiliation a
where a.date_added >= (select max_date from last_refreshed)
or a.date_modified >= (select max_date from last_refreshed)
);
我认为拥有一个计算 last_refreshed 日期并将其放入可重复使用的变量中的函数会更有意义并且更有效。所以我就那样做了。这是功能：
注意：你可以在这里看到我有时需要从不同的表中获取日期。这是通过 if/else 解释了上面的代码，我只是把它省略了，所以你不必阅读相同的代码 4 次。
function get_last_refreshed_date(scope in smallint) return date is
last_refreshed date;
table_name varchar2(30);
select_sql varchar2(255);
begin
if scope = c_scope_all then
table_name := 'ad.pbi_gvg_profile';
else
table_name := 'ad.pbi_gvg_profile_ag';
end if;
select_sql := 'select trunc(max(last_refreshed))
from '||table_name;
execute immediate select_sql
into last_refreshed;
return(last_refreshed);
end get_last_refreshed_date;
然后我改变光标的开头来使用这个函数和一个变量，所以现在它看起来像这样：
last_refreshed date := get_last_refreshed_date(scope);
cursor gvg_profile_c is
with modified_ids as
(
select distinct id_number
from ad.hr_giving cg
join ad.pbi_dates d
on d.DATE_FULL = trunc(cg.processed_date)
where d.RELATIVE_DATE >= last_refreshed
and d.RELATIVE_DATE <= trunc(CURRENT_DATE)
and cg.fiscal_year >= ad.current_fiscal_year - 6
union
select distinct gi.gift_donor_id as id_number
from ad.gift gi
where gi.date_added >= last_refreshed
or gi.date_modified >= last_refreshed
union
select distinct p.pledge_donor_id as id_number
from ad.pledge_rev p
where p.date_added >= last_refreshed
or p.date_modified >= last_refreshed
union
select distinct a.id_number
from ad.affiliation a
where a.date_added >= last_refreshed
or a.date_modified >= last_refreshed
),
这很好用。我的程序仍然只需要 5 分钟即可运行。
但是，当我对 Delete 语句进行相同的更改时，程序突然需要大约 65 分钟才能运行。从日志中我可以看出，删除语句的执行占了其中 60 多分钟。
为什么变量在游标中可以正常工作，但会导致过程主体中的 delete 语句严重变慢？
非常感谢任何帮助！