> ## 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.

# optimize_use_* 会话设置

> ClickHouse 中 optimize_use_* 生成组的会话设置。

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>;
};

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

<div id="optimize_use_implicit_projections">
  ## optimize\_use\_implicit\_projections
</div>

<SettingsInfoBlock type="Bool" default_value="1" />

自动选择隐式投影来执行 SELECT 查询

<div id="optimize_use_projection_filtering">
  ## optimize\_use\_projection\_filtering
</div>

<SettingsInfoBlock type="Bool" default_value="1" />

<VersionHistory rows={[{"id": "row-1","items": [{"label": "25.6"},{"label": "1"},{"label": "新设置"}]}]} />

即使未选择使用投影来执行 SELECT 查询，也允许利用投影对分片范围进行过滤。

<div id="optimize_use_projections">
  ## optimize\_use\_projections
</div>

**别名**: `allow_experimental_projection_optimization`

<SettingsInfoBlock type="Bool" default_value="1" />

启用或禁用处理 `SELECT` 查询时的[投影](/docs/zh/reference/engines/table-engines/mergetree-family/mergetree#projections)优化。

可选值：

* 0 — 已禁用投影优化。
* 1 — 已启用投影优化。