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

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vertical_merge_algorithm_min_bytes_to_activate

Minimal (approximate) uncompressed size in bytes in merging parts to activate Vertical merge algorithm.

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vertical_merge_algorithm_min_columns_to_activate

Minimal amount of non-PK columns to activate Vertical merge algorithm.

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vertical_merge_algorithm_min_rows_to_activate

Minimal (approximate) sum of rows in merging parts to activate Vertical merge algorithm.

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vertical_merge_optimize_lightweight_delete

If true, lightweight delete is optimized on vertical merge.

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vertical_merge_optimize_ttl_delete

If true, rows TTL delete is optimized on vertical merge. Instead of forcing horizontal merge, the TTL filter is evaluated and passed to the merging algorithm which sets skip flags in row sources.

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vertical_merge_remote_filesystem_prefetch

If true prefetching of data from remote filesystem is used for the next column during merge
Last modified on July 23, 2026