filesystem_cache_* session settings

These settings are available in system.settings and are autogenerated from source.

filesystem_cache_allow_background_download

Allow filesystem cache to enqueue background downloads for data read from remote storage. Disable to keep downloads in the foreground for the current query/session.

filesystem_cache_boundary_alignment

Filesystem cache boundary alignment. This setting is applied only for non-disk read (e.g. for cache of remote table engines / table functions, but not for storage configuration of MergeTree tables). Value 0 means no alignment.

filesystem_cache_enable_background_download_during_fetch

Only has an effect in ClickHouse Cloud. Wait time to lock cache for space reservation in filesystem cache

filesystem_cache_enable_background_download_for_metadata_files_in_packed_storage

Only has an effect in ClickHouse Cloud. Wait time to lock cache for space reservation in filesystem cache

filesystem_cache_max_download_size

Max remote filesystem cache size that can be downloaded by a single query

filesystem_cache_name

Filesystem cache name to use for stateless table engines or data lakes

filesystem_cache_prefer_bigger_buffer_size

Prefer bigger buffer size if filesystem cache is enabled to avoid writing small file segments which deteriorate cache performance. On the other hand, enabling this setting might increase memory usage.

filesystem_cache_reserve_space_wait_lock_timeout_milliseconds

Wait time to lock cache for space reservation in filesystem cache

filesystem_cache_segments_batch_size

Limit on size of a single batch of file segments that a read buffer can request from cache. Too low value will lead to excessive requests to cache, too large may slow down eviction from cache

filesystem_cache_skip_download_if_exceeds_per_query_cache_write_limit

Aliases: skip_download_if_exceeds_query_cache

Skip download from remote filesystem if exceeds query cache size

filesystem_cache_verbose_logging

Emit TEST-level log messages for every filesystem cache buffer refill (state of the read, remaining size to read, bytes read). Only for debugging: the messages are formatted once per read, so enabling it on a query that does many small cached reads adds a large amount of logging overhead. The messages are only visible when the log level is test anyway (see send_logs_level).

filesystem_cache_wait_for_concurrent_download_timeout_milliseconds

Maximum time to wait for a file segment which is being downloaded to the filesystem cache by a concurrent query. When the timeout is reached, the read bypasses the filesystem cache for that range and reads directly from remote storage, while the concurrent download continues to fill the cache. Value 0 means do not wait at all: bypass the cache immediately if the needed range is not downloaded yet. Lowering this value bounds the tail latency of cache-hit reads which would otherwise wait for another query’s download pace at the cost of additional requests to remote storage.