number_of_* MergeTree table settings

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

number_of_free_entries_in_pool_to_execute_mutation

When there is less than specified number of free entries in pool, do not execute part mutations. This is to leave free threads for regular merges and to avoid “Too many parts” errors.

Possible values:

• Any positive integer.

Usage

The value of the number_of_free_entries_in_pool_to_execute_mutation setting must not exceed the product of background_pool_size and background_merges_mutations_concurrency_ratio. Otherwise, ClickHouse will throw an exception.

number_of_free_entries_in_pool_to_execute_optimize_entire_partition

When there is less than specified number of free entries in pool, do not execute optimizing entire partition in the background (this task generated when set min_age_to_force_merge_seconds and enable min_age_to_force_merge_on_partition_only). This is to leave free threads for regular merges and avoid “Too many parts”.

Possible values:

• Positive integer.

The value of the number_of_free_entries_in_pool_to_execute_optimize_entire_partition setting must not exceed the product of background_pool_size and background_merges_mutations_concurrency_ratio. Otherwise, ClickHouse throws an exception.

number_of_free_entries_in_pool_to_lower_max_size_of_merge

When there is less than the specified number of free entries in pool (or replicated queue), start to lower maximum size of merge to process (or to put in queue). This is to allow small merges to process - not filling the pool with long running merges.

Possible values:

• Any positive integer.

number_of_mutations_to_delay

If table has at least that many unfinished mutations, artificially slow down mutations of table. Disabled if set to 0

number_of_mutations_to_throw

If table has at least that many unfinished mutations, throw ‘Too many mutations’ exception. Disabled if set to 0

number_of_partitions_to_consider_for_merge

Only available in ClickHouse Cloud. Up to top N partitions which we will consider for merge. Partitions picked in a random weighted way where weight is amount of data parts which can be merged in this partition.