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

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max_files_to_modify_in_alter_columns

Do not apply ALTER if number of files for modification(deletion, addition) is greater than this setting. Possible values:
  • Any positive integer.
Default value: 75

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max_files_to_remove_in_alter_columns

Do not apply ALTER, if the number of files for deletion is greater than this setting. Possible values:
  • Any positive integer.
Last modified on July 23, 2026