> ## Documentation Index
> Fetch the complete documentation index at: https://private-7c7dfe99-revert-104359-revert-104251-parquet-single.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# allow_experimental_* MergeTree 表设置

> 按 allow_experimental_* 自动生成分组的 ClickHouse MergeTree 表设置。

export const VersionHistory = ({rows = []}) => {
  if (rows.length === 0) {
    return null;
  }
  const headers = ["版本", "默认值", "注释"];
  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
  }}>
        版本历史
      </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
  }}>类型</div>
      <div style={{
    overflowWrap: "anywhere"
  }}>{type}</div>
      <div style={{
    fontWeight: 600,
    opacity: 0.72,
    marginInlineStart: "0.5rem"
  }}>默认值</div>
      <div style={{
    overflowWrap: "anywhere"
  }}>{default_value}</div>
      {changeable_without_restart && <div style={{
    fontWeight: 600,
    opacity: 0.72,
    marginInlineStart: "0.5rem"
  }}>
          无需重启即可更改
        </div>}
      {changeable_without_restart && <div style={{
    overflowWrap: "anywhere"
  }}>
          {changeable_without_restart}
        </div>}
    </div>;
};

export const ExperimentalBadge = () => {
  return <a href="https://clickhouse.com/docs/reference/settings/beta-and-experimental-features#experimental-features" className="experimentalBadge">
            <div className="experimentalIcon">
            <svg width="16" height="16" viewBox="0 0 16 16" fill="none" xmlns="http://www.w3.org/2000/svg">
                <path strokeWidth="1.25" d="M5.5 2H10.5" stroke="currentColor" strokeLinecap="round" strokeLinejoin="round" />
                <path strokeWidth="1.25" d="M9.50015 2V6.19625L13.4283 12.7425C13.4738 12.8183 13.4985 12.9049 13.4996 12.9934C13.5008 13.0818 13.4785 13.169 13.435 13.246C13.3914 13.323 13.3283 13.3871 13.2519 13.4317C13.1755 13.4764 13.0886 13.4999 13.0002 13.5H3.00015C2.91164 13.5 2.8247 13.4766 2.74822 13.432C2.67174 13.3874 2.60847 13.3233 2.56487 13.2463C2.52126 13.1693 2.49889 13.082 2.50004 12.9935C2.50119 12.905 2.52582 12.8184 2.5714 12.7425L6.50015 6.19625V2" stroke="currentColor" strokeLinecap="round" strokeLinejoin="round" />
                <path strokeWidth="1.25" d="M4.47656 9.56754C5.30344 9.41254 6.47656 9.47942 7.99969 10.25C10.0153 11.2707 11.4216 11.0569 12.2184 10.7282" stroke="currentColor" strokeLinecap="round" strokeLinejoin="round" />
            </svg>
        </div>
            Experimental 功能
        </a>;
};

这些设置可在 [system.merge\_tree\_settings](/zh/reference/system-tables/merge_tree_settings) 中查看，并由 ClickHouse 源代码自动生成。

<div id="allow_experimental_adaptive_codec_selection">
  ## allow\_experimental\_adaptive\_codec\_selection
</div>

<ExperimentalBadge />

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

<VersionHistory rows={[{"id": "row-1","items": [{"label": "26.8"},{"label": "0"},{"label": "新增设置"}]}]} />

启用后，合并和变更会为使用默认编解码器 (未指定 `CODEC` 子句，或指定了 `CODEC(Default)`) 的列逐块选择编解码器。
候选编解码器包括表的默认编解码器 (参见 `default_compression_codec` 设置) 、`NONE` 以及适合该列类型的专用编解码器。
目前仅整数类类型支持自适应选择。
输出最小的候选项将被选中。因此，压缩效果不会比默认编解码器更差，无法压缩的块会以原始形式存储。
如果某列的默认编解码器包含加密 (例如 `AES_128_GCM_SIV`) ，则不会对其进行自适应选择，以确保始终应用加密。
每个块使用的编解码器可通过 [`mergeTreeCodecBlockCounts`](/zh/reference/functions/table-functions/index) 表函数查看。

<div id="allow_experimental_replacing_merge_with_cleanup">
  ## allow\_experimental\_replacing\_merge\_with\_cleanup
</div>

<ExperimentalBadge />

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

允许对带有 `is_deleted`
列的 ReplacingMergeTree 执行实验性的 CLEANUP 合并。启用后，可使用 `OPTIMIZE ... FINAL CLEANUP` 手动
将一个分区中的所有 parts 合并为单个 part，并删除其中
已删除的行。

还允许通过设置 `min_age_to_force_merge_seconds`、
`min_age_to_force_merge_on_partition_only` 和
`enable_replacing_merge_with_cleanup_for_min_age_to_force_merge`
使这类合并在后台自动执行。

<div id="allow_experimental_reverse_key">
  ## allow\_experimental\_reverse\_key
</div>

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

<VersionHistory rows={[{"id": "row-1","items": [{"label": "24.12"},{"label": "0"},{"label": "新增设置"}]}]} />

已废弃的设置，不起任何作用。

<div id="allow_experimental_text_index_phrase_search">
  ## allow\_experimental\_text\_index\_phrase\_search
</div>

<ExperimentalBadge />

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

<VersionHistory rows={[{"id": "row-1","items": [{"label": "26.7"},{"label": "0"},{"label": "新增设置"}]}]} />

允许创建带有实验性 `support_phrase_search` 参数的文本索引，
该参数会存储标记位置，以支持精确的短语匹配。