[Need help] Handle joined tables filters

[SpencerMelo]

Description

Hi, I've being trying to properly use filters on joined tables, but did not found a way which feels correct, and need some direction.

Code

Given the following schema:

diesel::table! {
    tickets (id) {
        id -> Uuid,
        stage_id -> Uuid,
        title -> Varchar
        // more fields with many types
    }
}

diesel::table! {
    stages (id) {
        id -> Uuid,
        name -> Varchar
        // more fields with many types
    }
}

diesel::joinable!(tickets -> stages (stage_id));
diesel::allow_tables_to_appear_in_same_query!(stages, tickets);

And consider I have a GET endpoint which allow filtering by table columns:

GET /tickets?filter_by=stage&filter_term=new

And the function entry looks like this:

pub fn get_tickets(
    pool: Arc<Pool<ConnectionManager<PgConnection>>>,
    filter_by: String,
    filter_term: String,
) -> Result<Vec<Ticket>, Box<dyn Error>> {

    let mut query = tickets::table
        .into_boxed()
        .limit(limit as i64)
        .offset(offset as i64)
        .inner_join(stages::table);
    ...
}

So considering the function will get filter params like filter_by=name&filter_term=hello for all possible columns including joined, it should be able to map to the specific column type on which it should build the filter query.filter(name.eq('blabla') or query.filter(title.eq('blabla'), which can be Varchar, Integer, Timestampz, Nullable<T>.

Initially, before having the joins, I just mapped the table fields, which worked well handling tables without joins, but now with joins Idk if there is a ergonomic way of handling it, other than mapping every single field for every single join in all services layers...

The current mapping I have is this:

pub enum TicketColumn {
    Text(Box<dyn BoxableExpression<tickets::table, Pg, SqlType = Text>>),
    Timestamp(Box<dyn BoxableExpression<tickets::table, Pg, SqlType = Timestamptz>>),
    NullableTimestamp(
        Box<dyn BoxableExpression<tickets::table, Pg, SqlType = Nullable<Timestamptz>>>,
    ),
}

pub fn get_column(name: &str) -> TicketColumn {
    match name {
        "title" => TicketColumn::Text(Box::new(title)),
        "created_at" => TicketColumn::Timestamp(Box::new(created_at)),
        "deleted_at" => TicketColumn::NullableTimestamp(Box::new(deleted_at)),
        _ => {
            info!("Unknown column name: '{}', defaulting to 'title'", name);
            TicketColumn::Text(Box::new(title))
        }
    }
}