> ## 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.

# merge_selecting_* MergeTree 表设置

> ClickHouse MergeTree 表设置，属于自动生成的 merge_selecting_* 分组。

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>;
};

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

<div id="merge_selecting_sleep_ms">
  ## merge\_selecting\_sleep\_ms
</div>

<SettingsInfoBlock type="UInt64" default_value="5000" />

在未选中任何可合并的 parts 后，再次尝试选择用于合并的 parts 前的最短等待时间。将此设置调低会更频繁地触发 background\_schedule\_pool 中的选择任务，从而在大规模集群中向 ZooKeeper 发送大量请求

<div id="merge_selecting_sleep_slowdown_factor">
  ## merge\_selecting\_sleep\_slowdown\_factor
</div>

<SettingsInfoBlock type="Float" default_value="1.2" />

当没有可合并的内容时，merge selecting 任务的休眠时间会乘以此因子；分配到 merge 时，则会除以此因子