How to use custom struct with raw sql query

[bcba25]

Hello everyone. I got a question on raw queries. Haven’t found much on diesel’s documentation.

#[derive(Debug, QueryableByName)]
#[table_name = "products"]
struct Product {
    pub id: Uuid,
    pub user_id: Uuid,
    pub name: String,
    pub location: Option<GeogPoint>,
    pub distance: f64, <-- ERROR: cannot find type `distance` in module `products`, not found in `products`
}

const QUERY: &str = r#"SELECT "id", "user_id", "name", "location", ST_Distance(...) as "distance" FROM products WHERE ST_Distance(...) <= 1000 ORDER BY "distance" ASC"#; 
let products = diesel::sql_query(QUERY).load::<Product>(_connection);

I’m wondering how can I use my custom structs with diesel and raw queries. If I delete distance field from struct, it will compile and execute the query but I need to show distance as well, which does not exists on table and formed with a query itself. Could you suggest on this please

[weiznich]

I've moved this to the discussion part of the repository as this is not a bug report, but a question.
Otherwise see the documentation.

[bcba25]

@weiznich thanks and sorry for creating as a bug. Could you provide a simple example on how to do that ? Or probably a fix for my example. I believe it should be relatively simple but I didn't find a way to do that

[weiznich]

To cite from the documentation:

To derive this trait, Diesel needs to know the SQL type of each field. You can do this by either annotating your struct with #[table_name = "some_table"] (in which case the SQL type will be diesel::dsl::SqlTypeOf<table_name::column_name>), or by annotating each field with #[sql_type = "SomeType"].

(Bold by me)

That means you just need to annotate your distance field with some compatible sql type via #[sql_type = "…"]. I cannot give more details as it is unclear from your question what the ST_Distance(…) function actually returns.