Re: Unique constraint on field inside composite type.

On 08/17/2016 11:02 PM, Silk Parrot wrote:
> Hi,
>
> I am trying to model a social login application. The application can
> support multiple login providers. I am thinking of creating a custom
> type for each provider. e.g.
>
> CREATE TYPE system.google_user AS (
> email TEXT
> );
>
> CREATE TYPE system.facebook_user AS (
> id TEXT
> );
>
> And having user table like:
>
> CREATE TABLE user (
> uuid UUID PRIMARY KEY DEFAULT public.uuid_generate_v4(),
> google_user system.google_user,
> facebook_user system.facebook_user,
> UNIQUE (google_user.email)
> );
>
> However, the above create table query reports syntax error:
>
> ERROR: syntax error at or near "."
> LINE 10: UNIQUE (google_user.email)
>
> Is there a way to create unique constraint on a field inside composite type?

I tried David's suggestion:

(google_user).email

and that did not work, but it got me to thinking, so:

CREATE OR REPLACE FUNCTION public.comp_type_idx(google_user)
RETURNS character varying
LANGUAGE sql
AS $function$ SELECT $1.email $function$

CREATE TABLE test_user (
google_user google_user,
facebook_user facebook_user
);

create unique index g_u on test_user (comp_type_idx(google_user));

test=# insert into test_user values (ROW('email'), ROW(1));
INSERT 0 1

test=# insert into test_user values (ROW('email'), ROW(1));
ERROR: duplicate key value violates unique constraint "g_u"
DETAIL: Key (comp_type_idx(google_user))=(email) already exists.

test=# insert into test_user values (ROW('email2'), ROW(1));
INSERT 0 1

test=# select * from test_user ;
google_user | facebook_user
-------------+---------------
(email) | (1)
(email2) | (1)
(2 rows)

>
> --
> Regards
> Ryan

--
Adrian Klaver
adrian(dot)klaver(at)aklaver(dot)com