> ## 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.

# materialize_projections_* MergeTree 表设置

> ClickHouse 在 materialize_projections_* 生成组中的 MergeTree 表设置。

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.merge\_tree\_settings](/docs/zh/reference/system-tables/merge_tree_settings) 中查看，且由 ClickHouse 源代码自动生成。

<div id="materialize_projections_on_insert">
  ## materialize\_projections\_on\_insert
</div>

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

<VersionHistory rows={[{"id": "row-1","items": [{"label": "26.6"},{"label": "1"},{"label": "新设置"}]}]} />

启用后，INSERT 会创建包含投影的新 parts。
否则，可以通过显式执行 [MATERIALIZE PROJECTION](/docs/zh/reference/statements/alter/projection#materialize-projection) 创建，
或在 合并 期间通过 [materialize\_projections\_on\_merge](/docs/zh/reference/settings/merge-tree-settings/materialize-projections#materialize_projections_on_merge) 创建。

<div id="materialize_projections_on_merge">
  ## materialize\_projections\_on\_merge
</div>

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

<VersionHistory rows={[{"id": "row-1","items": [{"label": "26.6"},{"label": "0"},{"label": "新设置"}]}]} />

启用后，如果参与一次合并的所有源 parts 都缺少某个投影 (例如因为它们在插入时设置了 `materialize_projections_on_insert = 0`) ，合并时会重新构建该投影，从而使合并后的 part 包含该投影。

合并仍然只会组合具有相同投影集合的 parts。要将某个投影回填到所有现有 parts，请使用显式 [MATERIALIZE PROJECTION](/docs/zh/reference/statements/alter/projection#materialize-projection)。使用 [materialize\_projections\_on\_insert](/docs/zh/reference/settings/merge-tree-settings/materialize-projections#materialize_projections_on_insert) 执行 INSERT 时，也会创建投影。