> ## Documentation Index
> Fetch the complete documentation index at: https://private-7c7dfe99-detect-table-modification.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# table_* MergeTree table settings

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

export const VersionHistory = ({rows = []}) => {
  if (rows.length === 0) {
    return null;
  }
  const headers = ["Version", "Default value", "Comment"];
  const border = "1px solid rgba(128, 128, 128, 0.3)";
  const cell = {
    border,
    padding: "0.25rem 0.5rem",
    textAlign: "start",
    verticalAlign: "top"
  };
  return <details className="not-prose" style={{
    border,
    borderRadius: "0.5rem",
    margin: "0.5rem 0",
    padding: "0.5rem 0.75rem",
    fontSize: "0.8125rem",
    lineHeight: "1.125rem"
  }}>
      <summary style={{
    cursor: "pointer",
    fontWeight: 600,
    opacity: 0.72
  }}>
        Version history
      </summary>
      <table style={{
    borderCollapse: "collapse",
    width: "100%",
    margin: "0.5rem 0 0"
  }}>
        <thead>
          <tr>
            {headers.map(header => <th key={header} style={{
    ...cell,
    fontWeight: 600,
    opacity: 0.72
  }}>
                {header}
              </th>)}
          </tr>
        </thead>
        <tbody>
          {rows.map((row, row_index) => <tr key={row.id ?? row_index}>
              {(row.items ?? []).map((item, item_index) => <td key={item_index} style={{
    ...cell,
    overflowWrap: "anywhere"
  }}>
                  {item?.label}
                </td>)}
            </tr>)}
        </tbody>
      </table>
    </details>;
};

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](/reference/system-tables/merge_tree_settings) and are autogenerated from ClickHouse source.

<h2 id="table_disk">
  table\_disk
</h2>

<SettingsInfoBlock type="Bool" default_value="0" />

<VersionHistory rows={[{"id": "row-1","items": [{"label": "25.2"},{"label": "0"},{"label": "New setting"}]}]} />

This is table disk: the path/endpoint points to the table data, not the database data.
Supported for object-storage disks whose metadata lives on the object storage itself
(s3\_plain, s3\_plain\_rewritable, web, web\_index) and their cached variants. Encrypted
variants are supported only over the writable s3\_plain / s3\_plain\_rewritable disks, not
over the read-only web / web\_index disks.

<h2 id="table_readonly">
  table\_readonly
</h2>

<SettingsInfoBlock type="Bool" default_value="0" />

<VersionHistory rows={[{"id": "row-1","items": [{"label": "26.3"},{"label": "0"},{"label": "New setting to mark table as read-only, preventing inserts and modifications"}]}]} />

If set to true, the table is in read-only mode and performs no modifications on disk.

All foreground operations that would modify the table are rejected: inserts, mutations, `OPTIMIZE`, and the data-mutating partition commands
(`ATTACH`/`MOVE`/`DROP`/`DROP DETACHED`/`FETCH`/`REPLACE PARTITION`, as well as `MOVE PARTITION ... TO TABLE` targeting this table). Operations
that do not modify the table's data, such as `FREEZE`/`UNFREEZE` and `FORGET PARTITION`, remain allowed.

No background work is scheduled either: regular merges, TTL merges (`DELETE`/`MOVE`/recompression), recompression merges, background mutations,
and background part moves are all suppressed. As a consequence, a table with a TTL no longer reclaims or moves its expired data while this setting
is enabled.

The setting can always be toggled back with `ALTER TABLE ... MODIFY SETTING table_readonly = 0` (or `RESET SETTING`). It is not supported for `ReplicatedMergeTree`.