Description
Contains information about all filesystem cache settingsColumns
cache_name(String) — Cache namepath(String) — Cache directory pathmax_size(UInt64) — Maximum cache sizemax_elements(UInt64) — Maximum number of cache elements, e.g. file segments (limits number of files on filesystem)max_file_segment_size(UInt64) — Maximum size of a single file segmentboundary_alignment(UInt64) — File segment alignmentreserve_granularity(UInt64) — Maximum size to reserve ahead of the downloaded size of a file segment, to take the cache lock less often. Starts from 0 for each reader/writer and grows with its repeated reservations up to this value. 0 disables reserve-ahead.cache_on_write_operations(UInt8) — Enables write-through cache (cache on INSERT and MERGE)cache_policy(String) — Cache eviction policyslru_size_ratio(Float64) — SLRU cache policy size ratio of protected to probationary elementsbackground_download_threads(UInt64) — Number of background download threads. Value 0 disables background downloadbackground_download_queue_size_limit(UInt64) — Maximum number of file segments in the background download queue. Value 0 means no limit. Background download is disabled when background_download_threads is 0background_download_max_file_segment_size(UInt64) — Alignment-rounded prefetch threshold for an already-started segment, not a cap on total segment size. Below this size, background download fills up to the value rounded up to boundary_alignment. Once downloaded_size reaches it, background download continues up to downloaded_size rounded up to boundary_alignmentload_metadata_threads(UInt64) — Maximum number of threads used to load cache metadata at server startupload_metadata_asynchronously(UInt8) — Enables asynchronous loading of metadata on server startupkeep_free_space_size_ratio(Float64) — A ratio of free space which cache would try to uphold in the backgroundkeep_free_space_elements_ratio(Float64) — A ratio of free elements which cache would try to uphold in the backgroundkeep_free_space_remove_batch(UInt64) — A remove batch size of cache elements made by background thread which upholds free space/elements ratiokeep_free_space_eviction_threads(UInt64) — Number of threads which perform the actual file segment removal (filesystem deletion) for the background free space/elements ratio keeping. The single background thread collects eviction candidates and frees their priority queue entries, while these threads do the lock-free removal in parallelinvalidated_entries_cleanup_interval_ms(UInt64) — Idle interval in milliseconds of the background task which purges invalidated (lazily-removed) priority queue entriesinvalidated_entries_cleanup_threshold(UInt64) — Number of accumulated invalidated priority queue entries which triggers their background removalinvalidated_entries_cleanup_remove_batch(UInt64) — Maximum number of invalidated priority queue entries removed under a single write lock per background iterationenable_filesystem_query_cache_limit(UInt8) — Enable limiting maximum size of cache which can be written within a querycache_hits_threshold(UInt64) — Deprecated settingenable_bypass_cache_with_threshold(UInt8) — Undocumented. Not recommended for usebypass_cache_threshold(UInt64) — Undocumented. Not recommended for usewrite_cache_per_user_id_directory(UInt8) — Deprecated setting, ignored. The behavior is now determined automatically based on cache policyallow_dynamic_cache_resize(UInt8) — Allow dynamic resize of filesystem cachedynamic_resize_lock_wait_ms(UInt64) — Timeout in milliseconds to acquire the dynamic resize exclusive lock before skipping the resize attemptmax_size_ratio_to_total_space(Float64) — Ratio ofmax_sizeto total disk spaceskip_cache_on_disk_failure(UInt8) — If true, bypass filesystem cache operations silently on disk IO errors. If false (default), disk IO errors are propagated as startup failures.use_split_cache(UInt8) — Use separation of files to system/data.split_cache_ratio(Float64) — Ratio of system segment to total size of cache for split_cache.system_cache_extensions(String) — Comma-separated list of file extensions that are classified as system cache segments whenuse_split_cacheis enabled. When changed, existing cache entries remain in their previous segment type and are evicted naturally over time. Restart is required to change this setting.overcommit_eviction_evict_step(UInt64) — Eviction step in bytes for overcommit eviction policy. Used for keep_free_space_*_ratio settingscheck_cache_probability(Float64) — Works only for debug or sanitizer build. Checks cache correctness by going through all cache and checking state of each cache elementidle_client_ttl_sec(UInt64) — If non-zero and the cache policy tracks per-client usage, all cache entries that belong to a client (user_id) which has not been accessed for this many seconds are fully removed from the cache. Each access by the client refreshes the timer. Default is 1 week. Used by the distributed cache server.idle_client_check_interval_sec(UInt64) — How often the idle client eviction task runs, in seconds. Only meaningful whenidle_client_ttl_secis non-zero. 0 means an automatic value (max(1, idle_client_ttl_sec / 10)).idle_client_eviction_threads(UInt64) — Maximum number of threads used to purge idle clients’ cache. Only meaningful whenidle_client_ttl_secis non-zero.expose_prometheus_eviction_metrics(UInt8) — Expose Prometheus metrics for filesystem cache eviction activity (filesystem_cache_evictions_totaletc.). Off by default. Can be toggled at runtime viaSYSTEM RELOAD CONFIG.expose_prometheus_eviction_metrics_per_user(UInt8) — Additionally expose per-user-id eviction metrics. Requiresexpose_prometheus_eviction_metrics. Cardinality grows with distinct evicting users.drop_cache_threads(UInt64) — Maximum number of threads used to remove cache keys in parallel onSYSTEM DROP FILESYSTEM CACHE. Value 1 means the removal is performed by the query thread aloneis_initialized(UInt8) — Indicates whether cache was successfully initializedcurrent_size(UInt64) — Current cache sizecurrent_elements_num(UInt64) — Current cache elements (file segments) number