Method FileExists

include/fma-common/file_system.h:839–843

    }

    bool FileExists(const std::string& file) const override {
        // WARN() << "SQLFileSystem::FileExists(const std::string& file) return true directly";
        bool fake_res = true;
        return fake_res;
    }

    bool Mkdir(const std::string& dir) const override {
        throw std::runtime_error(