**Use case**

```
Received exception from server (version 21.11.1):
Code: 36. DB::Exception: Received from localhost:9000. DB::Exception: Wrong index name. Cannot find index `test_pentagram` to drop.. (BAD_ARGUMENTS)

github-explorer.ru-central1.internal :) ALTER TABLE hackernews DROP INDEX text_pentagram
```

It did not show me the typo.
struct TemporaryFiles
    {
        std::vector<std::unique_ptr<Poco::TemporaryFile>> files;
        size_t sum_size_uncompressed = 0;
        size_t sum_size_compressed = 0;
        mutable std::mutex mutex;
        bool empty() const
        {
            std::lock_guard lock(mutex);
            return files.empty();
        }
    };
    const TemporaryFiles & getTemporaryFiles() const { return temporary_files; }
    
    Block getHeader(bool final) const;
private: