[SOLVED] How to insert a SQL literal call to "NOW()" with diesel?

How to insert a SQL literal call to "NOW()" with diesel?

if I have a schema (psql) using fields TIMESTAMP (not tz, assume UTC for all times)

in rust i can represent them with

// schema.rs
diesel::table! {
    mytable (id) {
        id -> Int4,
        event_date -> Timestamp,
        ...
// models.rs
#[derive(Queryable, Selectable, Insertable)]
#[diesel(table_name = crate::database::schema::mytable)]
#[diesel(check_for_backend(diesel::pg::Pg))]
pub struct MyTable {
    pub id: i32,
    pub event_date: chrono::NaiveDateTime,
    ...

How can I insert/update a record, in a way that the resulting query will have a call to SQL's NOW(), such as: event_date=NOW()?

Solution

You obviously can't use your existing model to have the database insert the timestamp, it always includes a fixed and predetermined ¹ chrono::NaiveDateTime.

You can either

create a dedicated insertable:

#[derive(Insertable)]
#[diesel(table_name = crate::database::schema::mytable)]
#[diesel(check_for_backend(diesel::pg::Pg))]
pub struct MyTableNow {
    pub id: i32,
    pub event_date: diesel::dsl::now,
    ...

or just insert the values raw:

use crate::database::schema::mytable::dsl::*;
diesel::insert_into(mytable)
    .values((event_date.eq(diesel::dsl::now), …))
    …

diesel::dsl::now is in no way compatible with any dateTime type that I can use on a diesel model

I think you missed that diesel::dsl::now is a datetime type which you can use in a diesel model. It is trivially compatible with itself.

¹determined when you create the query in your program