I have a table which have 2 column, start date and end date.
I'm creating a trigger which ensure that no record overlap with the other ones, and so far I made this
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');
You can see that I'm testing all the overlap conditions one by one, the problem about a non-ending period I solved using a date up to year 9999, to make all working.
This code I'm sharing it's working, at the end of it you cand find a insert statement which ends with failure (related to the given case),
Those checks are a lot "manually", I'm wondering if this can be achieved with a query which uses intersect or similar but I haven't find a working approach
EDIT Based on @GMB approach, this is the final result
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;
In my actual scenario I also have a column which defines if the record is active or not, so I added a where clause in the definition. I also moved to a separate ADD CONSTRAINT statement because my table already exists, so I only add this one.
No need for complicated trigger code. You can do what you want simplify and efficiently with an exclusion constraint:
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 &&)
);
Argument [] to daterange() makes the range inclusive on both ends, which is how I understood your question.
Edit: if you want the exclusion to be based on another column, say 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 &&
)
);