min_absolute_delay_to_close
Minimal absolute delay to close, stop serving requests and not return Ok during status check.min_columns_to_activate_adaptive_write_buffer
Allow to reduce memory usage for tables with lots of columns by using adaptive writer buffers. Compared against the number of streams a wide part writes, which can greatly exceed its number of columns: aMap with many buckets, or a deeply nested Array or Tuple, writes many streams
for a single column, and one write buffer is allocated per stream.
Possible values:
- 0 - disabled
- 1 - always enabled
min_compress_block_size
Minimum size of blocks of uncompressed data required for compression when writing the next mark. You can also specify this setting in the global settings (see min_compress_block_size setting). The value specified when the table is created overrides the global value for this setting.min_index_granularity_bytes
Min allowed size of data granules in bytes. To provide a safeguard against accidentally creating tables with very lowindex_granularity_bytes.
min_marks_to_honor_max_concurrent_queries
The minimal number of marks read by the query for applying the max_concurrent_queries setting.Queries will still be limited by other
max_concurrent_queries settings.- Positive integer.
0— Disabled (max_concurrent_querieslimit applied to no queries).
min_merge_bytes_to_use_direct_io
The minimum data volume for merge operation that is required for using direct I/O access to the storage disk. When merging data parts, ClickHouse calculates the total storage volume of all the data to be merged. If the volume exceedsmin_merge_bytes_to_use_direct_io bytes, ClickHouse reads and writes the
data to the storage disk using the direct I/O interface (O_DIRECT option).
If min_merge_bytes_to_use_direct_io = 0, then direct I/O is disabled.
min_partition_age_to_force_merge_seconds
Merge parts in a partition if every part in it is older than this value, i.e. the partition no longer receives inserts. Unlikemin_age_to_force_merge_seconds with min_age_to_force_merge_on_partition_only,
the partition does not have to fit into a single merge: each merge still
respects max_bytes_to_merge_at_max_space_in_pool. Works for Simple and
StochasticSimple merge selectors.
The age compared here is the age of the youngest part in the partition
(now - modification_time, minimised over its parts), so the rule arms only
once every part has aged past this value. Any new part resets it: an insert, a
mutation, and also each merge this setting itself assigns, because the merged
part is new. Forcing therefore disarms as soon as a forced merge lands and
re-arms only after this value elapses again with no new parts, so a partition
that needs several merges is compacted over successive rounds spaced by this
interval rather than in one continuous pass.
Forcing works exactly like min_age_to_force_merge_seconds: it waives the
size-ratio requirement that normally keeps an unbalanced merge from being
assigned, and it also waives the min_parts_to_merge_at_once floor, so a
forced merge can cover fewer parts than that floor asks for. No other
heuristic is turned off: merge_selector_window_size still bounds which parts
are examined, and merge_selector_enable_heuristic_to_remove_small_parts_at_right
still trims a trailing small part from a selected range of three parts or more.
Either of those that a workload needs off must be turned off explicitly through
its own setting.
Under the Simple and StochasticSimple merge selectors, cannot be combined with
min_age_to_force_merge_seconds together with
min_age_to_force_merge_on_partition_only. That pair merges a whole partition
at once, and only such a merge is marked final, which is what lets a
ReplacingMergeTree run CLEANUP; forcing regular merges by partition age
would pre-empt it. Use the pair for partitions that fit into a single merge and
this setting for the ones that do not. Other selectors ignore this setting, so
the combination is accepted with them.
Possible values:
- Positive integer.
min_parts_to_merge_at_once
Minimal amount of data parts which merge selector can pick to merge at once (expert level setting, don’t change if you don’t understand what it is doing). 0 - disabled. Works for Simple and StochasticSimple merge selectors.min_replicated_logs_to_keep
Keep about this number of last records in ZooKeeper log, even if they are obsolete. It doesn’t affect work of tables: used only to diagnose ZooKeeper log before cleaning. Possible values:- Any positive integer.