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

# hdfs_* session settings

> ClickHouse session settings in the hdfs_* 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 available in [system.settings](/reference/system-tables/settings) and are autogenerated from [source](https://github.com/ClickHouse/ClickHouse/blob/master/src/Core/Settings.cpp).

<h2 id="hdfs_create_new_file_on_insert">
  hdfs\_create\_new\_file\_on\_insert
</h2>

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

Enables or disables creating a new file on each insert in HDFS engine tables. If enabled, on each insert a new HDFS file will be created with the name, similar to this pattern:

initial: `data.Parquet.gz` -> `data.1.Parquet.gz` -> `data.2.Parquet.gz`, etc.

Possible values:

* 0 — `INSERT` query appends new data to the end of the file.
* 1 — `INSERT` query creates a new file.

<h2 id="hdfs_ignore_file_doesnt_exist">
  hdfs\_ignore\_file\_doesnt\_exist
</h2>

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

<VersionHistory rows={[{"id": "row-1","items": [{"label": "24.6"},{"label": "0"},{"label": "Allow to return 0 rows when the requested files don't exist instead of throwing an exception in HDFS table engine"}]}]} />

Ignore absence of file if it does not exist when reading certain keys.

Possible values:

* 1 — `SELECT` returns empty result.
* 0 — `SELECT` throws an exception.

<h2 id="hdfs_replication">
  hdfs\_replication
</h2>

<SettingsInfoBlock type="UInt64" default_value="0" />

The actual number of replications can be specified when the hdfs file is created.

<h2 id="hdfs_skip_empty_files">
  hdfs\_skip\_empty\_files
</h2>

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

Enables or disables skipping empty files in [HDFS](/reference/engines/table-engines/integrations/hdfs) engine tables.

Possible values:

* 0 — `SELECT` throws an exception if empty file is not compatible with requested format.
* 1 — `SELECT` returns empty result for empty file.

<h2 id="hdfs_throw_on_zero_files_match">
  hdfs\_throw\_on\_zero\_files\_match
</h2>

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

<VersionHistory rows={[{"id": "row-1","items": [{"label": "24.6"},{"label": "0"},{"label": "Allow to throw an error when ListObjects request cannot match any files in HDFS engine instead of empty query result"}]}]} />

Throw an error if matched zero files according to glob expansion rules.

Possible values:

* 1 — `SELECT` throws an exception.
* 0 — `SELECT` returns empty result.

<h2 id="hdfs_truncate_on_insert">
  hdfs\_truncate\_on\_insert
</h2>

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

Enables or disables truncation before an insert in hdfs engine tables. If disabled, an exception will be thrown on an attempt to insert if a file in HDFS already exists.

Possible values:

* 0 — `INSERT` query appends new data to the end of the file.
* 1 — `INSERT` query replaces existing content of the file with the new data.