> ## 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.

# automatic_parallel_* 会话设置

> ClickHouse 在 automatic_parallel_* 自动生成分组中的会话设置。

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 <div 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。 <u><a href="/docs/docs/beta-and-experimental-features#experimental-features">了解详情。</a></u>
        </div>;
};

这些设置可在 [system.settings](/docs/zh/reference/system-tables/settings) 中找到，并由 [源文件](https://github.com/ClickHouse/ClickHouse/blob/master/src/Core/Settings.cpp) 自动生成。

<div id="automatic_parallel_replicas_min_bytes_per_replica">
  ## automatic\_parallel\_replicas\_min\_bytes\_per\_replica
</div>

<ExperimentalBadge />

<SettingsInfoBlock type="UInt64" default_value="1048576" />

<VersionHistory rows={[{"id": "row-1","items": [{"label": "26.1"},{"label": "1048576"},{"label": "根据测试结果调整后的更优默认值"}]}, {"id": "row-2","items": [{"label": "25.12"},{"label": "0"},{"label": "新设置"}]}]} />

用于自动启用并行副本的每个副本读取字节数阈值 (仅在 `automatic_parallel_replicas_mode`=1 时适用) 。0 表示不设阈值。
待读取的总字节数会根据已收集的统计信息进行估算。

<div id="automatic_parallel_replicas_mode">
  ## automatic\_parallel\_replicas\_mode
</div>

<ExperimentalBadge />

<SettingsInfoBlock type="UInt64" default_value="0" />

<VersionHistory rows={[{"id": "row-1","items": [{"label": "25.12"},{"label": "0"},{"label": "新设置"}]}]} />

根据已收集的统计信息，启用自动切换为使用并行副本执行。要求 `enable_analyzer = 1`、`enable_parallel_replicas != 0`、`parallel_replicas_local_plan = 1`，并提供 `cluster_for_parallel_replicas`。
0 - 禁用，1 - 启用，2 - 仅启用统计信息收集 (不切换为使用并行副本执行) 。