tiberius-mappers

Row mappers for the Tiberius SQL Server driver.

• Allows you to map tiberius rows to structs
• Defines FromRowBorrowed and FromRowOwned traits
• Supports deriving the FromRowBorrowed and FromRowOwned traits for structs via the tiberius-mappers-derive crate
• Handles null values where these map to Option fields in the struct
• Currently maps by name in FromRowBorrowed and by index in FromRowOwned

The existing tiberius-derive crate currently offers more options for mapping, but does not seem to be maintained and doesn't work with newer versions of Tiberius. I have been maintaining a fork of this crate to support newer versions of Tiberius in internal builds, but I wanted to start from scratch with a simpler implementation.

Usage

This is a work in progress. Currently, the FromRowBorrowed and FromRowOwned mapper is implemented.

#[derive(FromRowBorrowed)] // Derive the FromRowBorrowed trait on our struct
pub struct Customer<'a> {
    pub id: i32,
    pub first_name: &'a str,
    pub last_name: &'a str,
    pub description: Option<&'a str>,
}

pub async fn print_customers(pool: &Pool<ConnectionManager>) -> Result<(), Box<dyn error::Error>> {
    const SQL: &str = "select top 10 id, first_name, last_name, description from customers;";
    let mut conn = pool.get().await?;
    let rows = conn.query(SQL, &[]).await?.into_first_result().await?;
    // Now we can call the from_row_borrowed method on each row
    let customers: Vec<Customer> = rows.iter().map(Customer::from_row_borrowed).collect::<Result<Vec<Customer>, _>>()?;

    for customer in customers {
        println!("Customer: {} - {:?} - {:?}", customer.customer_code, customer.description, customer.dispatch_loc_id);
    }

    Ok(())
}

TODO

• Add more tests (proc macros are not as straightforward to test!)
• Decide whether to support mapping by index for borrowed rows
  • It may be cleaner to always map into owned types (i.e. remove FromRowBorrowed) and to always map by index (as it's faster) but with an option to validate the row names in the returned query result set against the struct field for safety
• Improve error messages
• Possibly support renaming fields (maybe, not sure if this is a good idea - would need to determine how this interacts with the decision about removing FromRowBorrowed as mentioned above)