allow_* MergeTree table settings

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

allow_coalescing_columns_in_partition_or_order_key

When enabled, allows coalescing columns in a CoalescingMergeTree table to be used in the partition or sorting key.

allow_commit_order_projection

Enables commit-order projections that store _block_number and _block_offset virtual columns, preserving original insertion order through merges. Requires enable_block_number_column and enable_block_offset_column to be enabled.

allow_dimensions_outside_sorting_key

In AggregatingMergeTree, background merges collapse rows that share the same value of the sorting key, combining their aggregate states. A column that is neither part of the sorting key nor an aggregate-state measure (AggregateFunction or SimpleAggregateFunction) is a dimension: after a merge it keeps an arbitrary value of one of the collapsed rows, which silently produces wrong results for queries that GROUP BY or filter on it (see https://github.com/ClickHouse/ClickHouse/issues/751).

By default, such a schema is rejected when the table is created. Enable this setting if the column is functionally dependent on the sorting key (so all collapsed rows share the same value) and the behavior is intentional.

The check applies only to tables that actually aggregate (those with at least one aggregate-state column) and is skipped when allow_tuple_element_aggregation is enabled.

allow_floating_point_partition_key

Enables to allow floating-point number as a partition key.

Possible values:

• 0 — Floating-point partition key not allowed.
• 1 — Floating-point partition key allowed.

allow_minmax_index_for_json

Allow creating minmax skip indexes on JSON (Object) columns. Disabled by default because the minmax index serialization path cannot handle heterogeneous Field values that JSON columns may contain.

allow_nullable_key

Allow Nullable types as primary keys.

allow_part_offset_column_in_projections

Allow usage of ‘_part_offset’ column in projections select query.

allow_reduce_blocking_parts_task

Background task which reduces blocking parts for shared merge tree tables. Only in ClickHouse Cloud

allow_remote_fs_zero_copy_replication

Don’t use this setting in production, because it is not ready.

allow_summing_columns_in_partition_or_order_key

When enabled, allows summing columns in a SummingMergeTree table to be used in the partition or sorting key.

allow_suspicious_indices

Reject primary/secondary indexes and sorting keys with identical expressions

allow_tuple_element_aggregation

When enabled, individual elements within Tuple columns participate in aggregation during merge in SummingMergeTree, AggregatingMergeTree, and CoalescingMergeTree. Nested Tuples are expanded recursively so that all leaf elements are aggregated independently. This setting is immutable and must be specified at table creation time.

allow_vertical_merges_from_compact_to_wide_parts

Allows vertical merges from compact to wide parts. This settings must have the same value on all replicas.