Re: How to reject overlapping timespans?

Quoth maps(dot)on(at)gmx(dot)net (Andreas):
> Am 17.02.2013 19:20, schrieb Andreas Kretschmer:
> > Andreas <maps(dot)on(at)gmx(dot)net> hat am 17. Februar 2013 um 18:02 geschrieben:
> >> I need to store data that has a valid timespan with start and enddate.
> >>
> >> objects ( id, name, ... )
> >> object_data ( object_id referencs objects(id), startdate, enddate, ... )
> >>
> >> nothing special, yet
> >>
> >> How can I have PG reject a data record where the new start- or enddate
> >> lies between the start- or enddate of another record regarding the same
> >> object_id?
> >
> > With 9.2 you can use DATERANGE and exclusion constraints
>
> though I still have a 9.1.x as productive server so I'm afraid I have to
> find another way.

If you don't fancy implementing or backporting a GiST operator class for
date ranges using OVERLAPS, you can fake one with the geometric types.
You will need contrib/btree_gist to get GiST indexes on integers.

create extension btree_gist;

create function point(date)
returns point
immutable language sql
as $$
select point(0, ($1 - date '2000-01-01')::double precision)
$$;

create function box(date, date)
returns box
immutable language sql
as $$
select box(point($1), point($2))
$$;

create table objects_data (
object_id integer references objects,
startdate date,
enddate date,
exclude using gist
(object_id with =, box(startdate, enddate) with &&)
);

You have to use 'box' rather than 'lseg' because there are no indexes
for lsegs. I don't know how efficient this will be, and of course the
unique index will probably not be any use for anything else.

Ben