Postgres的数组唯一约束 [英] Postgres UNIQUE CONSTRAINT for array

问题描述

如何在所有的值像阵列中的唯一性创建一个约束：

How to create a constraint on the uniqueness of all the values ​​in the array like:

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

我的排序功能

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; 

我需要的，这将是价值{10，22}和{22，10}视为相同，并在唯一约束检查​​

I need that would be the value {10, 22} and {22, 10} considered the same and check under the UNIQUE CONSTRAINT

推荐答案

我不认为你可以使用一个函数具有的唯一约束但你可以href=\"http://www.postgresql.org/docs/current/static/sql-createindex.html\">唯一一个首页的。因此，考虑一个排序功能是这样的：

I don't think you can use a function with a unique constraint but you can with a unique index. So given a sorting function something like this:

create function sort_array(integer[]) returns integer[] as $$
    select array_agg(n) from (select n from unnest($1) as t(n) order by n) as a;
$$ language sql immutable;

然后，你可以这样做：

Then you could do this:

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：

Then the following happens:

=> 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

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