postgresql唯一索引防止重叠

Question

我的表权限如下：

id serial,
person_id integer,
permission_id integer,
valid_from date,
valid_to date

我想防止创建与 valid_from、valid_to 日期重叠的权限

例如。

1 | 1 | 1 | 2010-10-01 | 2999-12-31
2 | 1 | 2 | 2010-10-01 | 2020-12-31
3 | 2 | 1 | 2015-10-01 | 2999-12-31

这个可以加：

4 | 1 | 3 | 2011-10-01 | 2999-12-31 - because no such permission
5 | 2 | 1 | 2011-10-10 | 2999-12-31 - because no such person
6 | 1 | 2 | 2021-01-01 | 2999-12-31 - because doesn't overlaps id:2

但这不能

7 | 1 | 1 | 2009-10-01 | 2010-02-01 - because overlaps id:1
8 | 1 | 2 | 2019-01-01 | 2022-12-31 - because overlaps id:2
9 | 2 | 1 | 2010-01-01 | 2016-12-31 - beacuse overlaps id:3

我可以进行外部检查，但想知道是否可以在数据库上进行检查

Answer 1

唯一约束基于相等运算符，在这种情况下不能使用，但您可以使用exclude constraint. 该约束使用 btree 运算符 <> 和 =，因此您必须安装 btree_gist extension.

create extension if not exists btree_gist;

create table permission(
    id serial,
    person_id integer,
    permission_id integer,
    valid_from date,
    valid_to date,
    exclude using gist (
        person_id with =, 
        permission_id with =, 
        daterange(valid_from, valid_to) with &&)
);

这些插入成功：

insert into permission values
    (1, 1, 1, '2010-10-01', '2999-12-31'),
    (2, 1, 2, '2010-10-01', '2020-12-31'),
    (3, 2, 1, '2015-10-01', '2999-12-31'),
    (4, 1, 3, '2011-10-01', '2999-12-31'),
    (5, 3, 1, '2011-10-10', '2999-12-31'), -- you meant person_id = 3 I suppose
    (6, 1, 2, '2021-01-01', '2999-12-31'),
    (7, 1, 1, '2009-10-01', '2010-02-01'); -- ranges do not overlap!

但这个不是：

insert into permission values
    (8, 1, 2, '2019-01-01', '2022-12-31');

ERROR:  conflicting key value violates exclusion constraint "permission_person_id_permission_id_daterange_excl"
DETAIL:  Key (person_id, permission_id, daterange(valid_from, valid_to))=(1, 2, [2019-01-01,2022-12-31)) conflicts with existing key (person_id, permission_id, daterange(valid_from, valid_to))=(1, 2, [2010-10-01,2020-12-31)).

在db<>fiddle.试试吧