Unique constraint on field inside composite type.

On Thu, Aug 18, 2016 at 2:02 AM, Silk Parrot <silkparrot@gmail.com> wrote:

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?

​Not tested here but in most (all?) cases when attempting to de-reference a
component of a composite typed column you must place the column name within
parentheses.

(google_user).email

Otherwise the system is thinking that "google_user" is a schema and email
is a column.

David J.​

On Wed, Aug 17, 2016 at 23:02:53 -0700,
Silk Parrot <silkparrot@gmail.com> 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 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)
);

Wouldn't it more sense to have a table you join to your user table that
is more flexible and allows for multiple entries per person. You would
need user, domain, foreign_user, auth_method. This would make it a lot
easier to add other systems later or let users pick their own systems
that you don't need to know about in advance.

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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.klaver@aklaver.com

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Adrian Klaver <adrian.klaver@aklaver.com> writes:

On 08/17/2016 11:02 PM, Silk Parrot wrote:

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)
);
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:

You'd need additional parens around the whole thing, like

create unique index on "user"(((google_user).email));

The UNIQUE-constraint syntax will never work, because per SQL standard
such constraints can only name simple columns. But you can make
a unique index separately.

regards, tom lane

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On 08/22/2016 06:23 PM, Tom Lane wrote:

Adrian Klaver <adrian.klaver@aklaver.com> writes:

On 08/17/2016 11:02 PM, Silk Parrot wrote:

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)
);
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:

You'd need additional parens around the whole thing, like

create unique index on "user"(((google_user).email));

Aah, I did not bury it deep enough, my attempt:

create unique index g_u on test_user ((google_user).email));

The UNIQUE-constraint syntax will never work, because per SQL standard
such constraints can only name simple columns. But you can make
a unique index separately.

regards, tom lane

--
Adrian Klaver
adrian.klaver@aklaver.com

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