apache/iceberg · error · UnsupportedOperationException

${this.getClass().getName()} doesn't implement fileLength

Error message

${this.getClass().getName()} doesn't implement fileLength

What it means

NativeEncryptionKeyMetadata.fileLength is a default method that throws UnsupportedOperationException. Implementations must override it to report the encrypted file length; the default exists so the interface can evolve without breaking existing implementations.

Source

Thrown at core/src/main/java/org/apache/iceberg/encryption/NativeEncryptionKeyMetadata.java:33

 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */
package org.apache.iceberg.encryption;

import java.nio.ByteBuffer;

/** {@link EncryptionKeyMetadata} for use with format-native encryption. */
public interface NativeEncryptionKeyMetadata extends EncryptionKeyMetadata {
  /** Encryption key as a {@link ByteBuffer} */
  ByteBuffer encryptionKey();

  /** Additional authentication data as a {@link ByteBuffer} */
  ByteBuffer aadPrefix();

  /** Encrypted file length */
  default Long fileLength() {
    throw new UnsupportedOperationException(
        this.getClass().getName() + " doesn't implement fileLength");
  }

  /**
   * Copy this key metadata and set the file length.
   *
   * @param length length of the encrypted file in bytes
   * @return a copy of this key metadata (key and AAD) with the file length
   */
  default NativeEncryptionKeyMetadata copyWithLength(long length) {
    throw new UnsupportedOperationException(
        this.getClass().getName() + " doesn't implement copyWithLength");
  }
}

View on GitHub (pinned to 86d9c8fc54)

Solutions

Override fileLength() in your NativeEncryptionKeyMetadata implementation to return the encrypted file length
Use copyWithLength on implementations that support it to obtain metadata carrying the length
Upgrade or patch the third-party key metadata implementation to one that implements fileLength

Example fix

// before
class MyKeyMetadata implements NativeEncryptionKeyMetadata { /* no fileLength */ }
// after
class MyKeyMetadata implements NativeEncryptionKeyMetadata {
  @Override public Long fileLength() { return encryptedLength; }
}

Defensive patterns

Strategy: try-catch

Validate before calling

try { km.fileLength(); return true; } catch (UnsupportedOperationException e) { return false; }

Type guard

boolean hasFileLength(NativeEncryptionKeyMetadata km) {
  try { return km.fileLength() != null; } catch (UnsupportedOperationException e) { return false; }
}

Try / catch

try { length = km.fileLength(); }
catch (UnsupportedOperationException e) { length = null; /* length unavailable */ }

Prevention

Override fileLength() in all custom NativeEncryptionKeyMetadata implementations
Test native encryption integrations against the current Iceberg interface
Prefer implementations from the Iceberg codebase over hand-rolled ones

When it happens

Trigger: Calling fileLength() on a NativeEncryptionKeyMetadata implementation that did not override the method — typically custom key metadata classes written before the method was added.

Common situations: Custom native encryption integrations (e.g. Parquet native encryption) with key metadata classes lacking the newer fileLength override; reading file lengths from third-party key metadata implementations.

Related errors

AI-assisted analysis of apache/iceberg@86d9c8fc54 (2026-09-12). Data as JSON: /api/errors/b2627eb985002d9e. Report an issue: GitHub.