fn generate_scan_expressions()

in src/data.rs [1397:1445]

• 40 lines of code
• 10 McCabe index (conditional complexity)

fn generate_scan_expressions(
    ts: &app::TableSchema,
    attributes: &Option<String>,
    keys_only: bool,
) -> GeneratedScanParams {
    // Early return for the default condition. no --keys-only, no --attributes.
    if !keys_only && attributes.is_none() {
        return GeneratedScanParams {
            exp: None,
            names: None,
        };
    }

    // dynein always shows primary key(s) i.e. pk and sk (if any).
    let mut names = HashMap::<String, String>::new();
    names.insert(String::from("#DYNEIN_PKNAME"), ts.clone().pk.name);
    let mut returning_attributes: Vec<String> = vec![String::from("#DYNEIN_PKNAME")];
    if let Some(sk) = &ts.sk {
        returning_attributes.push(String::from("#DYNEIN_SKNAME"));
        names.insert(String::from("#DYNEIN_SKNAME"), sk.clone().name);
    };

    // if keys_only flag is true, no more attribute would be added.
    if keys_only {
    } else if let Some(_attributes) = attributes {
        let mut i: usize = 0;
        let attrs: Vec<&str> = _attributes.split(',').map(|x| x.trim()).collect();
        for attr in attrs {
            // skip if attributes contain primary key(s) as they're already included in the expression.
            if attr == ts.pk.name || (ts.sk.is_some() && attr == ts.clone().sk.unwrap().name) {
                continue;
            }

            let placeholder = String::from("#DYNEIN_ATTRNAME") + &i.to_string();
            returning_attributes.push(placeholder.clone());
            names.insert(placeholder, String::from(attr));
            i += 1;
        }
    };

    let expression: String = returning_attributes.join(",");
    debug!("generated ProjectionExpression: {}", &expression);
    debug!("generated ExpressionAttributeNames: {:?}", &names);

    GeneratedScanParams {
        exp: Some(expression),
        names: Some(names),
    }
}