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

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max_parts_in_total

If the total number of active parts in all partitions of a table exceeds the max_parts_in_total value INSERT is interrupted with the Too many parts (N) exception. Possible values:
  • Any positive integer.
A large number of parts in a table reduces performance of ClickHouse queries and increases ClickHouse boot time. Most often this is a consequence of an incorrect design (mistakes when choosing a partitioning strategy - too small partitions).

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max_parts_to_merge_at_once

Max amount of parts which can be merged at once (0 - disabled). Doesn’t affect OPTIMIZE FINAL query.
Last modified on July 23, 2026