> ## Documentation Index
> Fetch the complete documentation index at: https://clickhouse.com/docs/llms.txt
> Use this file to discover all available pages before exploring further.

# object_shared_* MergeTree table settings

> ClickHouse MergeTree table settings in the object_shared_* generated group.

export const SettingsInfoBlock = ({type, default_value, changeable_without_restart}) => {
  return <div className="not-prose" style={{
    display: "flex",
    flexWrap: "wrap",
    alignItems: "baseline",
    columnGap: "0.5rem",
    rowGap: "0.125rem",
    margin: "0.375rem 0",
    fontSize: "0.8125rem",
    lineHeight: "1.125rem"
  }}>
      <div style={{
    fontWeight: 600,
    opacity: 0.72
  }}>Type</div>
      <div style={{
    overflowWrap: "anywhere"
  }}>{type}</div>
      <div style={{
    fontWeight: 600,
    opacity: 0.72,
    marginInlineStart: "0.5rem"
  }}>Default</div>
      <div style={{
    overflowWrap: "anywhere"
  }}>{default_value}</div>
      {changeable_without_restart && <div style={{
    fontWeight: 600,
    opacity: 0.72,
    marginInlineStart: "0.5rem"
  }}>
          Changeable without restart
        </div>}
      {changeable_without_restart && <div style={{
    overflowWrap: "anywhere"
  }}>
          {changeable_without_restart}
        </div>}
    </div>;
};

These settings are available in [system.merge\_tree\_settings](/docs/reference/system-tables/merge_tree_settings) and are autogenerated from ClickHouse source.

<h2 id="object_shared_data_buckets_for_compact_part">
  object\_shared\_data\_buckets\_for\_compact\_part
</h2>

<SettingsInfoBlock type="NonZeroUInt64" default_value="8" />

<VersionHistory rows={[{"id": "row-1","items": [{"label": "25.8"},{"label": "8"},{"label": "Add a setting to control number of buckets for shared data in JSON serialization in compact parts"}]}]} />

The number of buckets for JSON shared data serialization in Compact parts. Works with `map_with_buckets` and `advanced` shared data serializations.
The maximum allowed value is 256.

<h2 id="object_shared_data_buckets_for_wide_part">
  object\_shared\_data\_buckets\_for\_wide\_part
</h2>

<SettingsInfoBlock type="NonZeroUInt64" default_value="32" />

<VersionHistory rows={[{"id": "row-1","items": [{"label": "25.8"},{"label": "32"},{"label": "Add a setting to control number of buckets for shared data in JSON serialization in wide parts"}]}]} />

The number of buckets for JSON shared data serialization in Wide parts. Works with `map_with_buckets` and `advanced` shared data serializations.
The maximum allowed value is 256.

<h2 id="object_shared_data_serialization_version">
  object\_shared\_data\_serialization\_version
</h2>

<SettingsInfoBlock type="MergeTreeObjectSharedDataSerializationVersion" default_value="advanced" />

<VersionHistory rows={[{"id": "row-1","items": [{"label": "25.8"},{"label": "map"},{"label": "Add a setting to control JSON serialization versions"}]}, {"id": "row-2","items": [{"label": "25.12"},{"label": "advanced"},{"label": "Enable advanced shared data serialization version by default"}]}]} />

Serialization version for shared data inside JSON data type.

Possible values:

* `map` - store shared data as `Map(String, String)`
* `map_with_buckets` - store shared data as several separate `Map(String, String)` columns. Using buckets improves reading individual paths from shared data.
* `advanced` - special serialization of shared data designed to significantly improve reading of individual paths from shared data.
  Note that this serialization increases the shared data storage size on disk because we store a lot of additional information.

The number of buckets for `map_with_buckets` and `advanced` serializations is determined by settings
[object\_shared\_data\_buckets\_for\_compact\_part](/docs/reference/settings/merge-tree-settings/object-shared#object_shared_data_buckets_for_compact_part)/[object\_shared\_data\_buckets\_for\_wide\_part](/docs/reference/settings/merge-tree-settings/object-shared#object_shared_data_buckets_for_wide_part).

<h2 id="object_shared_data_serialization_version_for_zero_level_parts">
  object\_shared\_data\_serialization\_version\_for\_zero\_level\_parts
</h2>

<SettingsInfoBlock type="MergeTreeObjectSharedDataSerializationVersion" default_value="map_with_buckets" />

<VersionHistory rows={[{"id": "row-1","items": [{"label": "25.8"},{"label": "map"},{"label": "Add a setting to control JSON serialization versions  for zero level parts"}]}, {"id": "row-2","items": [{"label": "25.12"},{"label": "map_with_buckets"},{"label": "Enable map_with_buckets shared data serialization version for zero level parts by default"}]}]} />

This setting allows to specify different serialization version of the
shared data inside JSON type for zero level parts that are created during inserts.
It's recommended not to use `advanced` shared data serialization for zero level parts because it can increase
the insertion time significantly.