> ## Documentation Index
> Fetch the complete documentation index at: https://private-7c7dfe99-revert-104359-revert-104251-parquet-single.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# format_schema_* format settings

> ClickHouse format settings in the format_schema_* generated group.

export const VersionHistory = ({rows = []}) => {
  if (rows.length === 0) {
    return null;
  }
  const headers = ["Version", "Default value", "Comment"];
  const border = "1px solid rgba(128, 128, 128, 0.3)";
  const cell = {
    border,
    padding: "0.25rem 0.5rem",
    textAlign: "start",
    verticalAlign: "top"
  };
  return <details className="not-prose" style={{
    border,
    borderRadius: "0.5rem",
    margin: "0.5rem 0",
    padding: "0.5rem 0.75rem",
    fontSize: "0.8125rem",
    lineHeight: "1.125rem"
  }}>
      <summary style={{
    cursor: "pointer",
    fontWeight: 600,
    opacity: 0.72
  }}>
        Version history
      </summary>
      <table style={{
    borderCollapse: "collapse",
    width: "100%",
    margin: "0.5rem 0 0"
  }}>
        <thead>
          <tr>
            {headers.map(header => <th key={header} style={{
    ...cell,
    fontWeight: 600,
    opacity: 0.72
  }}>
                {header}
              </th>)}
          </tr>
        </thead>
        <tbody>
          {rows.map((row, row_index) => <tr key={row.id ?? row_index}>
              {(row.items ?? []).map((item, item_index) => <td key={item_index} style={{
    ...cell,
    overflowWrap: "anywhere"
  }}>
                  {item?.label}
                </td>)}
            </tr>)}
        </tbody>
      </table>
    </details>;
};

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 are autogenerated from [source](https://github.com/ClickHouse/ClickHouse/blob/master/src/Core/FormatFactorySettings.h).

<h2 id="format_schema">
  format\_schema
</h2>

This parameter is useful when you are using formats that require a schema definition, such as [Cap'n Proto](https://capnproto.org/) or [Protobuf](https://developers.google.com/protocol-buffers/). The value depends on the format.

<h2 id="format_schema_message_name">
  format\_schema\_message\_name
</h2>

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

Define the name of the required message in the schema defined in `format_schema`.
To maintain compatibility with the legacy format\_schema format (`file_name:message_name`):

* If `format_schema_message_name` is not specified, the message name is inferred from the `message_name` part of the legacy `format_schema` value.
* If `format_schema_message_name` is specified while using the legacy format, an error will be raised.

<h2 id="format_schema_source">
  format\_schema\_source
</h2>

<SettingsInfoBlock type="String" default_value="file" />

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

Define the source of `format_schema`.
Possible values:

* 'file' (default): The `format_schema` is the name of a schema file located in the `format_schemas` directory.
* 'string': The `format_schema` is the literal content of the schema.
* 'query': The `format_schema` is a query to retrieve the schema.
  When `format_schema_source` is set to 'query', the following conditions apply:
* The query must return exactly one value: a single row with a single string column.
* The result of the query is treated as the schema content.
* This result is cached locally in the `format_schemas` directory.
* You can clear the local cache using the command: `SYSTEM DROP FORMAT SCHEMA CACHE FOR Files`.
* Once cached, identical queries from the same user are not executed to fetch the schema again until the cache is explicitly cleared
* In addition to local cache files, Protobuf messages are also cached in memory. Even after clearing the local cache files, the in-memory cache must be cleared using `SYSTEM DROP FORMAT SCHEMA CACHE [FOR Protobuf]` to fully refresh the schema.
* Run the query `SYSTEM DROP FORMAT SCHEMA CACHE` to clear the cache for both cache files and Protobuf messages schemas at once.
* The query is executed on behalf of the user running it, so it is subject to that user's access rights, and its cached result is reused only for the same user. It cannot be executed where there is no user: in a background task, such as a streaming engine consumer, or when `INSERT` data is parsed on the client side. Use `format_schema_source` set to `file` or `string` there.