Date: Fri, 3 Aug 2012 07:40:17 +0200
From: Andreas Kretschmer <akretschmer@spamfence.net>
To: pgsql-sql@postgresql.org
Subject: Re: can this be done with a check expression?
Message-ID: <20120803054016.GA7909@tux>
References: <20120802231043.GA16173@slacker.ja10629.home>
	<29693.1343949814@sss.pgh.pa.us>
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Tom Lane <tgl@sss.pgh.pa.us> wrote:

> Wayne Cuddy <lists-pgsql@useunix.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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