Automated updated_at set to NOW()

[marthvon]

Yeah, pretty much bunch of macros and traits that allow me to automatically append NOW() on timestamp/timestamptz of updated_at attribute/field every time diesel::update is called on table. Just running into a few issues concerning the update_statement module being private and no other way to get SetNotCalled, SetCalled outside of the module to define UpdateStatement generic types. Given I have a bunch of tables with created_at, updated_at... I thought this would be a cool feature to work on. And, Yes, Alternatively, would have been easier to just write sql triggers... But I've invested too much time on this for it to not work.

use diesel::expression::Expression;
//use diesel::query_builder::update_statement::{SetNotCalled, SetCalled}; // !!! update_statement is private module !!!
use diesel::query_builder::{AsChangeset, IntoUpdateTarget, UpdateStatement};
use diesel::sql_types::{Timestamp, Timestamptz};
use diesel::{Column, QuerySource, dsl, prelude::*};

/**
 * For Postgres Type Timestamptz
 * Use case ex.
 *  use crate::traits::HasUpdatedAt;
 *  --- For the `users` table ---
 *  impl HasUpdatedAt for users::table {
 *    type UpdatedAtColumn = users::updated_at;
 *    const UPDATED_AT_COLUMN: Self::UpdatedAtColumn = users::updated_at;
 *  }
 */
pub trait HasUpdatedAtTz: diesel::Table {
  type UpdatedAtColumn: Column + Expression<SqlType = Timestamptz> + Send + Sync + 'static;
  const UPDATED_AT_COLUMN: Self::UpdatedAtColumn;
}

/**
 * For Postgres Type Timestamptz
 * Use case ex.
 * impl AutoUpdatedAt for <Model struct> {};
 */
pub trait AutoUpdatedAtDslTz<'a, Changes>
where
  Changes: AsChangeset,
{
  type Output;
  fn change_now(self, changes: &'a Changes) -> Self::Output;
}

impl<'a, T, Tab, Changes> AutoUpdatedAtDslTz<'a, Changes> for UpdateStatement<T, Tab, SetNotCalled>
where
  &'a Changes: AsChangeset,
  T: IntoUpdateTarget<Table = Tab>,
  Tab: HasUpdatedAtTz,
{
  type Output = UpdateStatement<T, Tab, SetCalled, (&'a Changes, dsl::Eq<Tab::UpdatedAtColumn, dsl::now>)>;
  fn change_now(self, changes: &'a Changes) -> Self::Output {
    self.set((
      changes,
      Tab::UPDATED_AT_COLUMN.eq(dsl::sql::<Timestamptz>("NOW()")),
    ))
  }
}

pub trait AutoUpdatedAtTz {
  fn change_now_on<'a, T, Tab>(
    &'a self,
    update_statement: UpdateStatement<T, Tab, SetNotCalled>,
  ) -> UpdateStatement<T, Tab, SetCalled, (&'a Self, dsl::Eq<Tab::UpdatedAtColumn, dsl::now>)>
  where
    &'a Self: AsChangeset,
    T: IntoUpdateTarget<Table = Tab> + QuerySource,
    Tab: HasUpdatedAtTz,
  {
    update_statement.change_now(self)
  }
}

/**
 * For Postgres Type Timestamp
 * Use case ex.
 *  use crate::traits::HasUpdatedAt;
 *  --- For the `users` table ---
 *  impl HasUpdatedAt for users::table {
 *    type UpdatedAtColumn = users::updated_at;
 *    const UPDATED_AT_COLUMN: Self::UpdatedAtColumn = users::updated_at;
 *  }
 */
pub trait HasUpdatedAt: diesel::Table {
  type UpdatedAtColumn: Column + Expression<SqlType = Timestamp> + Send + Sync + 'static;
  const UPDATED_AT_COLUMN: Self::UpdatedAtColumn;
}

/**
 * For Postgres Type Timestamp
 * Use case ex.
 * impl AutoUpdatedAt for <Model struct> {};
 */
pub trait AutoUpdatedAtDsl<'a, Changes>
where
  Changes: AsChangeset,
{
  type Output;
  fn change_now(self, changes: &'a Changes) -> Self::Output;
}

impl<'a, T, Tab, Changes> AutoUpdatedAtDsl<'a, Changes> for UpdateStatement<T, Tab, SetNotCalled>
where
  &'a Changes: AsChangeset,
  T: IntoUpdateTarget<Table = Tab>,
  Tab: HasUpdatedAt,
{
  type Output = UpdateStatement<T, Tab, SetCalled, (&'a Changes, dsl::Eq<Tab::UpdatedAtColumn, dsl::now>)>;
  fn change_now(self, changes: &'a Changes) -> Self::Output {
    self.set((changes, Tab::UPDATED_AT_COLUMN.eq(dsl::now)))
  }
}

pub trait AutoUpdatedAt {
  fn change_now_on<'a, T, Tab>(
    &'a self,
    update_statement: UpdateStatement<T, Tab, SetNotCalled>,
  ) -> UpdateStatement<T, Tab, SetCalled, (&'a Self, dsl::Eq<Tab::UpdatedAtColumn, dsl::now>)>
  where
    &'a Self: AsChangeset,
    T: IntoUpdateTarget<Table = Tab> + QuerySource,
    Tab: HasUpdatedAt,
  {
    update_statement.change_now(self)
  }
}

[weiznich]

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