Diesel allows to mix aggregate and unaggregate expressions via `ORDER BY` clauses

[weiznich]

Setup

Versions

• Rust: 1.83.0
• Diesel: 2.2.6
• Database: Postgresql 16.3
• Operating System Fedora

Feature Flags

• diesel: postgres

Problem Description

use diesel::prelude::*;

diesel::table! {
    users {
        id -> Integer,
        name -> Text,
    }
}

fn main() {
    let mut conn = PgConnection::establish("postgres://localhost/diesel_tests").unwrap();
    users::table
        .select(diesel::dsl::max(users::id))
        .order_by(users::name)
        .load::<Option<i32>>(&mut conn)
        .unwrap();
}

What are you trying to accomplish?

Build a query that uses ORDER BY and aggregate functions

What is the expected output?

The compilation fails as the query is invalid

What is the actual output?

Compilation succeeds, but the application fails to run the query with the following message:

thread 'main' panicked at src/main.rs:16:10:
called `Result::unwrap()` on an `Err` value: DatabaseError(Unknown, "column \"users.name\" must appear in the GROUP BY clause or be used in an aggregate function")

Steps to reproduce

Run the code above

Checklist

• I have already looked over the issue tracker and the discussion forum for similar possible closed issues.

• This issue can be reproduced on Rust's stable channel. (Your issue will be
  closed if this is not the case)
• This issue can be reproduced without requiring a third party crate

[ayarotsky]

@weiznich do you mind if I take care of this one?

[weiznich]

@ayarotsky Sure feel free to have a look. If you get stuck please ask questions