with_entry_keys.rs

match cache.entry(sql) {
    Occupied(entry) => Ok(entry.get().clone()),
    Vacant(entry) => {
        let statement = try!(Statement::prepare(&self.raw_connection, entry.key()));
        Ok(entry.insert(CachedStatement::new(statement)).clone())
    }
}

without_entry_keys.rs

if cache.contains_key(&sql) {
    Ok(cache[&sql].clone())
} else {
    let statement = try!(Statement::prepare(&self.raw_connection, &sql));
    let entry = cache.entry(sql);
    Ok(entry.or_insert(CachedStatement::new(statement)).clone())
}