[英]Postgres trigger to check date overlap with already existing records
我有一個表,有 2 列,開始日期和結束日期。
我正在創建一個觸發器,以確保沒有記錄與其他記錄重疊,到目前為止我做了這個
DROP TABLE IF EXISTS public.working_hours;
CREATE TABLE public.working_hours (
id serial NOT NULL,
date_start date NOT NULL,
date_end date NULL
);
-- Insert some valid data
INSERT INTO public.working_hours (date_start,date_end) VALUES ('2020-12-10'::date,'2020-12-20'::date);
-- Setup trigger to check
create or REPLACE FUNCTION check_date_overlap()
RETURNS trigger as
$body$
declare
temprow record;
a date;
b date;
c date;
d date;
begin
c := new.date_start;
d := new.date_end;
if d is null -- End date is optional
then
d := '9999-12-31'::date;
end if;
for temprow in
SELECT *
FROM public.working_hours
WHERE id != new.id -- Avoid the record itself which is under update
ORDER BY date_start
loop
a := temprow.date_start;
b := temprow.date_end;
if b is null -- End date is optional
then
b := '9999-12-31'::date;
end if;
/*
* temprow: A-------------B
* new: C----D
*/
if a < c and b > d
then
RAISE EXCEPTION 'case A: record is overlapping with record %', temprow.id;
end if;
/*
* temprow: A----B
* new: C-------------D
*/
if a > c and b < d
then
RAISE EXCEPTION 'case B: record is overlapping with record %', temprow.id;
end if;
/*
* tn: A-------------B
* new: C-------------D
*/
if a < c and c < b and b < d
then
RAISE EXCEPTION 'case C: record is overlapping with record %', temprow.id;
end if;
/*
* temprow: A-------------B
* new: C-------------D
*/
if c < a and a < d and d < b
then
RAISE EXCEPTION 'case D: record is overlapping with record %', temprow.id;
end if;
/*
* temprow: A-------------B
* new: C-------------D
*/
if c < a and a = d and d < b
then
RAISE EXCEPTION 'case E: record is overlapping with record %', temprow.id;
end if;
/*
* temprow: A-------------B
* new: C-------------D
*/
if a < c and b = c and b < d
then
RAISE EXCEPTION 'case F: record is overlapping with record %', temprow.id;
end if;
end loop;
RETURN NEW;
end
$body$
LANGUAGE plpgsql;
drop trigger if exists on_check_date_overlap on public.working_hours;
create trigger on_check_date_overlap
before update or insert
on public.working_hours
for each row
execute procedure check_date_overlap();
-- Test case A fail
-- INSERT INTO public.working_hours (date_start,date_end) VALUES ('2020-12-15','2020-12-18');
-- Test case B fail
-- INSERT INTO public.working_hours (date_start,date_end) VALUES ('2020-12-5','2020-12-25');
-- Test case C fail
-- INSERT INTO public.working_hours (date_start,date_end) VALUES ('2020-12-15','2020-12-25');
-- Test case D fail
-- INSERT INTO public.working_hours (date_start,date_end) VALUES ('2020-12-5','2020-12-15');
-- Test case E fail
-- INSERT INTO public.working_hours (date_start,date_end) VALUES ('2020-12-5','2020-12-10');
-- Test case F fail
-- INSERT INTO public.working_hours (date_start,date_end) VALUES ('2020-12-20','2020-12-25');
-- Test success
-- INSERT INTO public.working_hours (date_start,date_end) VALUES ('2020-12-21','2020-12-25');
你可以看到我正在一個一個地測試所有的重疊條件,這個關於我使用 9999 年之前的日期解決的非結束時間段的問題,以使所有工作正常。
我分享的這段代碼正在工作,在它的最后你可以找到一個以失敗結尾的插入語句(與給定的情況有關),
這些檢查很多是“手動”的,我想知道這是否可以通過使用 intersect 或類似的查詢來實現,但我還沒有找到可行的方法
編輯基於@GMB 方法,這是最終結果
DROP TABLE IF EXISTS public.working_hours;
CREATE TABLE public.working_hours (
id serial NOT NULL,
status varchar(255) not null,
user_id int NOT null,
date_start date NOT NULL,
date_end date NULL
);
alter table public.working_hours
ADD CONSTRAINT prevent_overlap
EXCLUDE USING gist (user_id WITH =, daterange(date_start, coalesce(date_end, 'infinity'), '[]') WITH &&)
where (status = 'active')
;
-- Insert some valid data
INSERT INTO public.working_hours (status, user_id, date_start,date_end) VALUES ('active', 1, '2020-12-10'::date,'2020-12-20'::date);
INSERT INTO public.working_hours (status, user_id, date_start,date_end) VALUES ('deleted', 1, '2020-12-5'::date,'2020-12-15'::date);
INSERT INTO public.working_hours (status, user_id, date_start,date_end) VALUES ('active', 2, '2020-12-10'::date,'2020-12-20'::date);
-- Updating from deleted to active will fail
update public.working_hours set status = 'active' where id = 2;
在我的實際場景中,我還有一列定義記錄是否處於活動狀態,因此我在定義中添加了 where 子句。 我還移到了單獨的ADD CONSTRAINT
語句,因為我的表已經存在,所以我只添加了這個。
無需復雜的觸發代碼。 您可以使用排除約束來簡化和有效地做您想做的事情:
CREATE TABLE public.working_hours (
id serial NOT NULL,
date_start date NOT NULL,
date_end date NULL,
EXCLUDE USING gist (daterange(date_start, coalesce(date_end, 'infinity'), '[]') WITH &&)
);
daterange()
的參數[]
使范圍在兩端都包含在內,這就是我理解您的問題的方式。
編輯:如果您希望排除基於另一列,請說user_id
:
CREATE TABLE public.working_hours (
id serial NOT NULL,
user_id int NOT NULL
date_start date NOT NULL,
date_end date NULL,
EXCLUDE USING gist (
user_id WITH =,
daterange(date_start, coalesce(date_end, 'infinity'), '[]') WITH &&
)
);
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