These settings are available in system.merge_tree_settings and are autogenerated from ClickHouse source.
shared_merge_tree_activate_coordinated_merges_tasks
Activates rescheduling of coordinated merges tasks. It can be useful even when
shared_merge_tree_enable_coordinated_merges=0 because this will populate merge coordinator
statistics and help with cold start.
Enables creation of per-replica /metadata and /columns nodes in ZooKeeper.
Only available in ClickHouse Cloud
shared_merge_tree_disable_merges_and_mutations_assignment
Stop merges assignment for shared merge tree. Only available in ClickHouse
Cloud
shared_merge_tree_empty_partition_lifetime
How many seconds partition will be stored in keeper if it has no parts.
shared_merge_tree_enable_automatic_empty_partitions_cleanup
Enabled cleanup of Keeper entries of empty partition.
shared_merge_tree_enable_coordinated_merges
Enables coordinated merges strategy
Enables writing attributes into virtual parts and committing blocks in keeper
shared_merge_tree_enable_outdated_parts_check
Enable outdated parts check. Only available in ClickHouse Cloud
shared_merge_tree_idle_parts_update_seconds
Interval in seconds for parts update without being triggered by ZooKeeper
watch in the shared merge tree. Only available in ClickHouse Cloud
shared_merge_tree_inactive_replica_cutoff_seconds
For how long an inactive replica is still taken into account by the background cleanup
(OutdatedPartsQuorumThread): while a replica has been inactive for less than this many seconds,
it still holds back removal of outdated parts and truncation of finished mutations. A value of 0
means use the default of two ZooKeeper session timeouts.
Only in ClickHouse Cloud
shared_merge_tree_initial_parts_update_backoff_ms
Initial backoff for parts update. Only available in ClickHouse Cloud
shared_merge_tree_interserver_http_connection_timeout_ms
Timeouts for interserver HTTP connection. Only available in ClickHouse Cloud
shared_merge_tree_interserver_http_timeout_ms
Timeouts for interserver HTTP communication. Only available in ClickHouse
Cloud
shared_merge_tree_leader_update_period_random_add_seconds
Add uniformly distributed value from 0 to x seconds to
shared_merge_tree_leader_update_period to avoid thundering
herd effect. Only available in ClickHouse Cloud
shared_merge_tree_leader_update_period_seconds
Maximum period to recheck leadership for parts update. Only available in
ClickHouse Cloud
shared_merge_tree_max_outdated_parts_to_process_at_once
Maximum amount of outdated parts leader will try to confirm for removal at
one HTTP request. Only available in ClickHouse Cloud.
shared_merge_tree_max_parts_update_backoff_ms
Max backoff for parts update. Only available in ClickHouse Cloud
shared_merge_tree_max_parts_update_leaders_in_total
Maximum number of parts update leaders. Only available in ClickHouse Cloud
shared_merge_tree_max_parts_update_leaders_per_az
Maximum number of parts update leaders. Only available in ClickHouse Cloud
shared_merge_tree_max_replicas_for_parts_deletion
Max replicas which will participate in parts deletion (killer thread). Only
available in ClickHouse Cloud
shared_merge_tree_max_replicas_to_merge_parts_for_each_parts_range
Max replicas which will try to assign potentially conflicting merges (allow
to avoid redundant conflicts in merges assignment). 0 means disabled. Only
available in ClickHouse Cloud
shared_merge_tree_max_suspicious_broken_parts
Max broken parts for SMT, if more - deny automatic detach.
shared_merge_tree_max_suspicious_broken_parts_bytes
Max size of all broken parts for SMT, if more - deny automatic detach.
shared_merge_tree_memo_ids_remove_timeout_seconds
How long we store insert memoization ids to avoid wrong actions during
insert retries. Only available in ClickHouse Cloud
shared_merge_tree_merge_coordinator_distribution_algorithm
What algorithm will be used by merge coordinator thread to distribute merges between replicas
shared_merge_tree_merge_coordinator_election_check_period_ms
Time between runs of merge coordinator election thread
shared_merge_tree_merge_coordinator_factor
Time changing factor for delay of coordinator thread
How often merge coordinator should sync with zookeeper to take fresh metadata
shared_merge_tree_merge_coordinator_max_merge_request_size
Number of merges that coordinator can request from MergerMutator at once
shared_merge_tree_merge_coordinator_max_period_ms
Maximum time between runs of merge coordinator thread
shared_merge_tree_merge_coordinator_merges_prepare_count
Number of merge entries that coordinator should prepare and distribute across workers.
When set to ‘auto’, equals the max number of merge tasks allowed on a single replica multiplied by the number of active replicas.
shared_merge_tree_merge_coordinator_min_period_ms
Minimum time between runs of merge coordinator thread
shared_merge_tree_merge_worker_fast_timeout_ms
Timeout that merge worker thread will use if it is needed to update it’s state after immediate action
shared_merge_tree_merge_worker_regular_timeout_ms
Time between runs of merge worker thread
shared_merge_tree_outdated_parts_group_size
How many replicas will be in the same rendezvous hash group for outdated parts cleanup.
Only available in ClickHouse Cloud.
shared_merge_tree_partitions_hint_ratio_to_reload_merge_pred_for_mutations
Will reload merge predicate in merge/mutate selecting task when <candidate partitions for mutations only (partitions that cannot be merged)>/<candidate partitions for mutations> ratio is higher than the setting. Only available
in ClickHouse Cloud
shared_merge_tree_parts_load_batch_size
Amount of fetch parts metadata jobs to schedule at once. Only available in
ClickHouse Cloud
shared_merge_tree_postpone_next_merge_for_locally_merged_parts_ms
Time to keep a locally merged part without starting a new merge containing
this part. Gives other replicas a chance fetch the part and start this merge.
Only available in ClickHouse Cloud.
shared_merge_tree_postpone_next_merge_for_locally_merged_parts_rows_threshold
Minimum size of part (in rows) to postpone assigning a next merge just after
merging it locally. Only available in ClickHouse Cloud.
shared_merge_tree_range_for_merge_window_size
Window size (in block numbers) used to distribute merge assignment across
replicas. Parts within the same window are assigned to the same replicas.
Only available in ClickHouse Cloud
shared_merge_tree_read_virtual_parts_from_leader
Read virtual parts from leader when possible. Only available in ClickHouse
Cloud
shared_merge_tree_replica_set_max_lifetime_seconds
How often replicas will try to update replica set in background. Next run is jittered
uniformly in [0, value] seconds. Exception: value = 0 does not follow that contract;
the implementation applies a minimum of 200 ms, so the next run is jittered in [0, 200] ms.
shared_merge_tree_try_fetch_part_in_memory_data_from_replicas
If enabled all the replicas try to fetch part in memory data (like primary
key, partition info and so on) from other replicas where it already exists.
shared_merge_tree_try_fetch_part_in_memory_data_from_replicas_on_startup
If enabled all the replicas try to fetch part in memory data (like primary
key, partition info and so on) on startup from other replicas where it already exists.
shared_merge_tree_update_replica_flags_delay_ms
How often replica will try to reload it’s flags according to background schedule.
Enables requesting FS cache hints from in-memory
cache on other replicas. Only available in ClickHouse Cloud
Use compact format for outdated parts: reduces load to Keeper, improves
outdated parts processing. Only available in ClickHouse Cloud
shared_merge_tree_use_too_many_parts_count_from_virtual_parts
If enabled too many parts counter will rely on shared data in Keeper, not on
local replica state. Only available in ClickHouse Cloud
shared_merge_tree_use_zookeeper_connection_pool
If enabled, SharedMergeTree uses one of server-level pooled ZooKeeper sessions.
shared_merge_tree_virtual_parts_discovery_batch
How many partition discoveries should be packed into batch
shared_merge_tree_virtual_parts_partition_atomic_discovery
Will SMT discover virtual parts partition atomically with extra data fetch and watches setup. Last modified on July 23, 2026
