Re: can this be done with a check expression?

Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:

> Wayne Cuddy <lists-pgsql(at)useunix(dot)net> writes:
> A less bogus way of doing things is to use an EXCLUDE constraint,
> although that will restrict you to be running PG 9.0 or newer. You
> also need some way of representing the ranges as indexable objects.
> In 9.0 or 9.1, probably the best way is to use contrib/seg/ to
> represent the ranges as line segments. 9.2 will have a cleaner
> solution, ie range types.

Simple example for 9.2:

test=# create table foo (name text, id_range int4range, exclude using gist(name with =, id_range with &&));
NOTICE: CREATE TABLE / EXCLUDE will create implicit index "foo_name_id_range_excl" for table "foo"
CREATE TABLE
Time: 40,273 ms
test=*# insert into foo values ('name1', '[1,9)');
INSERT 0 1
Time: 0,660 ms
test=*# insert into foo values ('name1', '[10,19)');
INSERT 0 1
Time: 0,313 ms
test=*# insert into foo values ('name1', '[5,15)');
ERROR: conflicting key value violates exclusion constraint "foo_name_id_range_excl"
DETAIL: Key (name, id_range)=(name1, [5,15)) conflicts with existing key (name, id_range)=(name1, [1,9)).
test=!#

Great feature! Thx to all developers behing PG!

Andreas
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