> ## 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.

# primary_index_* server settings

> ClickHouse server settings in the primary_index_* 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 configure the ClickHouse server and are autogenerated from ClickHouse source.

<h2 id="primary_index_cache_policy">
  primary\_index\_cache\_policy
</h2>

<SettingsInfoBlock type="String" default_value="SLRU" changeable_without_restart="No" />Primary index cache policy name.

<h2 id="primary_index_cache_prewarm_ratio">
  primary\_index\_cache\_prewarm\_ratio
</h2>

<SettingsInfoBlock type="Double" default_value="0.95" changeable_without_restart="No" />The ratio of total size of mark cache to fill during prewarm.

<h2 id="primary_index_cache_size">
  primary\_index\_cache\_size
</h2>

<SettingsInfoBlock type="UInt64" default_value="5368709120" changeable_without_restart="Yes" />Maximum size of cache for primary index (index of MergeTree family of tables).

<h2 id="primary_index_cache_size_ratio">
  primary\_index\_cache\_size\_ratio
</h2>

<SettingsInfoBlock type="Double" default_value="0.5" changeable_without_restart="No" />The size of the protected queue (in case of SLRU policy) in the primary index cache relative to the cache's total size.