INSERT DEFAULT VALUES?

[KeenS]

I have this table

CREATE TABLE users
(
	id serial NOT NULL,
	created_at timestamp DEFAULT CURRENT_TIMESTAMP NOT NULL,
	PRIMARY KEY (id)
) WITHOUT OIDS;

and want to create an user using default values.

I tried to define this structure:

#[derive(Insertable)]
#[table_name="users"]
pub struct NewUser {}

but it raises this error:

error: no rules expected the token `]`
  --> model/src/lib.rs:23:19
   |
23 | #[derive(Insertable)]
   |                   ^

It is reasonable because in SQL, inserting empty values is not allowed

db=# insert into users () values (); 
ERROR:  syntax error at or near ")"  
LINE 1: insert into users () values (); 

However, with, DEFAULT VALUE you can insert values with default values.

actcast=# INSERT INTO users DEFAULT VALUES;
INSERT 0 1
actcast=# SELECT * FROM USERS;
 id |         created_at
----+----------------------------
  1 | 2017-04-26 01:12:56.90735
(1 row)

How can I use this feature through diesel? Or if not supported, could you support this (feature request)?

[KeenS]

Of cause, I know I can do it with sql function

sql::<Integer>("INSERT INTO users DEFAULT VALUES RETURNING id")

[sgrif]

This is a reasonable feature, but I'm unsure what I'd like the public API for it to be. If nothing else, #[derive(Insertable)] with no columns should fail to compile, as we're breaking our guarantees about runtime errors.

[KeenS]

I suppose allowing empty structs to derive Insertable (in that case, empty structs will use DEFAULT VALUES) or providing another function like insert_defaults() will do.