Repository: tikv/tikv
File: components/sst_importer/src/sst_importer.rs (Rust)

Code before:
                Err(e)
            }
        }
    }

    pub async fn download_files_ext(
        &self,
        basic_meta: &SstMeta,
        metas: &HashMap<String, SstMeta>,
        backend: &StorageBackend,
        rewrite_rule: &RewriteRule,
        crypter: Option<CipherInfo>,
        speed_limiter: Limiter,
        engine: E,
        ext: DownloadExt<'_>,
    ) -> Result<Option<Range>> {
        debug!("download start";
            "metas" => ?basic_meta,
            "url" => ?backend,
            "rewrite_rule" => ?rewrite_rule,
            "speed_limit" => speed_limiter.speed_limit(),
        );
        let mut sst_readers = Vec::new();
        let clean_paths = Mutex::new(Vec::new());
        defer! {
            for path in clean_paths.lock().unwrap().iter_mut() {
                self.remove_file_no_throw(&path)
            }
        };
        for (name, meta) in metas {
            let path = self.dir.join_for_write(meta)?;
            let dst_file_name = self
                .do_download_sst_file(
                    &path,
                    meta,
                    backend,
                    name,
                    crypter.clone(),
                    &speed_limiter,
                    ext.cache_key.unwrap_or(""),
                )
                .await?;
            // now validate the SST file.
            let env = get_env(self.key_manager.clone(), get_io_rate_limiter())?;
            // Use abstracted SstReader after Env is abstracted.
            let sst_reader = RocksSstReader::open_with_env(&dst_file_name, Some(env))?;
            sst_reader.verify_checksum()?;

            sst_readers.push(sst_reader);
            clean_paths.lock().unwrap().push(path.temp);
        }

Review comment (performance):
Using `iter_mut()` is unnecessary here since the paths are not being mutated. Consider using `iter()` instead, which would be more semantically accurate and potentially more efficient.
```suggestion
            for path in clean_paths.lock().unwrap().iter() {
```

Code after:
                Err(e)
            }
        }
    }

    pub async fn download_files_ext(
        &self,
        basic_meta: &SstMeta,
        metas: &HashMap<String, SstMeta>,
        backend: &StorageBackend,
        rewrite_rule: &RewriteRule,
        crypter: Option<CipherInfo>,
        speed_limiter: Limiter,
        engine: E,
        ext: DownloadExt<'_>,
    ) -> Result<Option<Range>> {
        debug!("download start";
            "metas" => ?basic_meta,
            "url" => ?backend,
            "rewrite_rule" => ?rewrite_rule,
            "speed_limit" => speed_limiter.speed_limit(),
        );
        let mut sst_readers = Vec::new();
        let clean_paths = Mutex::new(Vec::new());
        defer! {
            for path in clean_paths.lock().unwrap().iter() {
                self.remove_file_no_throw(path)
            }
        };
        for (name, meta) in metas {
            let path = self.dir.join_for_write(meta)?;
            let dst_file_name = self
                .do_download_sst_file(
                    &path,
                    meta,
                    backend,
                    name,
                    crypter.clone(),
                    &speed_limiter,
                    ext.cache_key.unwrap_or(""),
                )
                .await?;
            // now validate the SST file.
            let env = get_env(self.key_manager.clone(), get_io_rate_limiter())?;
            // Use abstracted SstReader after Env is abstracted.
            let sst_reader = RocksSstReader::open_with_env(&dst_file_name, Some(env))?;
            sst_reader.verify_checksum()?;

            sst_readers.push(sst_reader);
            clean_paths.lock().unwrap().push(path.temp);
        }