With a large volume of queries per second logging all queries gets expensive, it would be nice to be able to log only a configurable fraction of the queries, selected at random.
/** Set multiple settings from "profile" (in server configuration file (users.xml), profiles contain groups of multiple settings).
     * The profile can also be set using the `set` functions, like the profile setting.
     */
    void setProfile(const String & profile_name, const Poco::Util::AbstractConfiguration & config);
    /// 
    void loadSettingsFromConfig(const String & path, const Poco::Util::AbstractConfiguration & config);
    /// 
    void dumpToMapColumn(IColumn * column, bool changed_only = true);
    /// 
    /// 
    void addProgramOptions(boost::program_options::options_description & options);
    /// 
    /// 
    static void checkNoSettingNamesAtTopLevel(const Poco::Util::AbstractConfiguration & config, const String & config_path);
};
/*
 * User-specified file format settings for File and URL engines.
 */
DECLARE_SETTINGS_TRAITS(FormatFactorySettingsTraits, FORMAT_FACTORY_SETTINGS)
struct FormatFactorySettings : public BaseSettings<FormatFactorySettingsTraits>
{
};
}