shared_merge_* MergeTree table settings

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

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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.

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shared_merge_tree_blobs_list_inline_file_max_bytes

Store files of a blob-list part that are at most this many bytes long (e.g. count.txt, metadata_version.txt, minmax indexes) directly inside the consolidated blobs.list file instead of a separate object-storage blob, saving one blob write and read per small file. 0 disables inlining. Takes effect only for parts using the blob-list storage (see shared_merge_tree_use_blobs_list_for_parts). Only available in ClickHouse Cloud.

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shared_merge_tree_create_per_replica_metadata_nodes

Enables creation of per-replica /metadata and /columns nodes in ZooKeeper. Only available in ClickHouse Cloud

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shared_merge_tree_disable_merges_and_mutations_assignment

Stop merges assignment for shared merge tree. Only available in ClickHouse Cloud

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shared_merge_tree_empty_partition_lifetime

How many seconds partition will be stored in keeper if it has no parts.

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shared_merge_tree_enable_automatic_empty_partitions_cleanup

Enabled cleanup of Keeper entries of empty partition.

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shared_merge_tree_enable_coordinated_merges

Enables coordinator-driven merge assignment for SharedMergeTree. The merge coordinator prepares merge entries and distributes them among active merge workers instead of relying only on independent merge selection.

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shared_merge_tree_enable_keeper_parts_extra_data

Enables writing attributes into virtual parts and committing blocks in keeper

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shared_merge_tree_enable_outdated_parts_check

Enables the SharedMergeTree background check that detects data parts which are no longer current and passes them to the parts-update process. Only available in ClickHouse Cloud.

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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

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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

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shared_merge_tree_initial_parts_update_backoff_ms

Initial delay, in milliseconds, before retrying a SharedMergeTree parts-update operation. Repeated retries increase the delay up to shared_merge_tree_max_parts_update_backoff_ms. Only available in ClickHouse Cloud.

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shared_merge_tree_interserver_http_connection_timeout_ms

Timeouts for interserver HTTP connection. Only available in ClickHouse Cloud

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shared_merge_tree_interserver_http_timeout_ms

Timeouts for interserver HTTP communication. Only available in ClickHouse Cloud

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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

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shared_merge_tree_leader_update_period_seconds

Maximum period to recheck leadership for parts update. Only available in ClickHouse Cloud

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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.

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shared_merge_tree_max_parts_update_backoff_ms

Maximum delay, in milliseconds, between retries of a SharedMergeTree parts-update operation. Only available in ClickHouse Cloud.

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shared_merge_tree_max_parts_update_leaders_in_total

Maximum number of replicas across the service that may concurrently hold the parts-update leader role. Only available in ClickHouse Cloud.

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shared_merge_tree_max_parts_update_leaders_per_az

Maximum number of replicas within one availability zone that may concurrently hold the parts-update leader role. Both this limit and shared_merge_tree_max_parts_update_leaders_in_total apply. Only available in ClickHouse Cloud.

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shared_merge_tree_max_replicas_for_parts_deletion

Max replicas which will participate in parts deletion (killer thread). Only available in ClickHouse Cloud

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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

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shared_merge_tree_max_suspicious_broken_parts

Max broken parts for SMT, if more - deny automatic detach.

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shared_merge_tree_max_suspicious_broken_parts_bytes

Max size of all broken parts for SMT, if more - deny automatic detach.

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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

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shared_merge_tree_merge_coordinator_distribution_algorithm

The algorithm used by the merge coordinator thread to distribute merges between replicas. Possible values:

• water_filling
• sainte_lague

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shared_merge_tree_merge_coordinator_election_check_period_ms

Time between runs of merge coordinator election thread

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shared_merge_tree_merge_coordinator_factor

Time changing factor for delay of coordinator thread

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shared_merge_tree_merge_coordinator_fetch_fresh_metadata_period_ms

How often merge coordinator should sync with zookeeper to take fresh metadata

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shared_merge_tree_merge_coordinator_max_merge_request_size

Number of merges that coordinator can request from MergerMutator at once

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shared_merge_tree_merge_coordinator_max_period_ms

Maximum time between runs of merge coordinator thread

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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.

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shared_merge_tree_merge_coordinator_min_period_ms

Minimum time between runs of merge coordinator thread

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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

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shared_merge_tree_merge_worker_regular_timeout_ms

Time between runs of merge worker thread

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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.

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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

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shared_merge_tree_parts_load_batch_size

Amount of fetch parts metadata jobs to schedule at once. Only available in ClickHouse Cloud

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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.

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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.

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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

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shared_merge_tree_read_virtual_parts_from_leader

Read virtual parts from leader when possible. Only available in ClickHouse Cloud

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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.

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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.

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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.

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shared_merge_tree_update_replica_flags_delay_ms

How often replica will try to reload it’s flags according to background schedule.

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shared_merge_tree_use_blobs_list_for_parts

Store parts of a SharedMergeTree table (both Wide and Compact) as a single consolidated blob-list metadata node instead of one Keeper node per file. Collapses per-part Keeper metadata from O(files) to a small constant while keeping one object-storage blob per file. Only available in ClickHouse Cloud.

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shared_merge_tree_use_metadata_hints_cache

Enables requesting FS cache hints from in-memory cache on other replicas. Only available in ClickHouse Cloud

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shared_merge_tree_use_outdated_parts_compact_format

Use compact format for outdated parts: reduces load to Keeper, improves outdated parts processing. Only available in ClickHouse Cloud

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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

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shared_merge_tree_use_zookeeper_connection_pool

If enabled, SharedMergeTree uses one of server-level pooled ZooKeeper sessions.

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shared_merge_tree_virtual_parts_discovery_batch

How many partition discoveries should be packed into batch

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shared_merge_tree_virtual_parts_partition_atomic_discovery

Obsolete setting, does nothing.