arrays - 数组的 Postgres 唯一约束

Question

如何对数组中所有值的唯一性创建约束，例如:

CREATE TABLE mytable
(
    interface integer[2],
    CONSTRAINT link_check UNIQUE (sort(interface))
)

我的排序函数

create or replace function sort(anyarray)
returns anyarray as $$
select array(select $1[i] from generate_series(array_lower($1,1),
array_upper($1,1)) g(i) order by 1)
$$ language sql strict immutable; 

我需要将值 {10, 22} 和 {22, 10} 视为相同并在 UNIQUE CONSTRAINT 下检查

Answer 1

我不认为你可以使用带有 unique constraint 的函数但你可以用 unique index .所以给定一个这样的排序函数:

create function sort_array(anyarray) returns anyarray as $$
    select array_agg(distinct n order by n) from unnest($1) as t(n);
$$ language sql immutable;

然后你可以这样做:

create table mytable (
    interface integer[2] 
);
create unique index mytable_uniq on mytable (sort_array(interface));

然后会发生以下情况:

=> insert into mytable (interface) values (array[11,23]);
INSERT 0 1
=> insert into mytable (interface) values (array[11,23]);
ERROR:  duplicate key value violates unique constraint "mytable_uniq"
DETAIL:  Key (sort_array(interface))=({11,23}) already exists.
=> insert into mytable (interface) values (array[23,11]);
ERROR:  duplicate key value violates unique constraint "mytable_uniq"
DETAIL:  Key (sort_array(interface))=({11,23}) already exists.
=> insert into mytable (interface) values (array[42,11]);
INSERT 0 1