ConfigurationPtrusers_config;/// Config with the users, profiles and quotas sections.
InterserverIOHandlerinterserver_io_handler;/// Handler for interserver communication.
std::optional<BackgroundSchedulePool>buffer_flush_schedule_pool;/// A thread pool that can do background flush for Buffer tables.
std::optional<BackgroundSchedulePool>schedule_pool;/// A thread pool that can run different jobs in background (used in replicated tables)
std::optional<BackgroundSchedulePool>distributed_schedule_pool;/// A thread pool that can run different jobs in background (used for distributed sends)
mutablestd::optional<BackgroundSchedulePool>buffer_flush_schedule_pool;/// A thread pool that can do background flush for Buffer tables.
mutablestd::optional<BackgroundSchedulePool>schedule_pool;/// A thread pool that can run different jobs in background (used in replicated tables)
mutablestd::optional<BackgroundSchedulePool>distributed_schedule_pool;/// A thread pool that can run different jobs in background (used for distributed sends)
MultiVersion<Macros>macros;/// Substitutions extracted from config.
std::unique_ptr<DDLWorker>ddl_worker;/// Process ddl commands from zk.
/// Rules for selecting the compression settings, depending on the size of the part.