apache/iceberg · error · UnsupportedOperationException

Cannot read unknown manifest type: %s

Error message

Cannot read unknown manifest type: %s

What it means

ManifestFiles.open() dispatches on the manifest's content type and only handles DATA and DELETES manifests. Any other ManifestContent value (or null from a stale/older reader that does not know the type) falls through to this UnsupportedOperationException.

Source

Thrown at core/src/main/java/org/apache/iceberg/ManifestFiles.java:424

   *
   * @param manifestData the binary data.
   * @return a {@link ManifestFile}. To be precise, it's a {@link GenericManifestFile} which don't
   *     expose to public.
   * @throws IOException if encounter any IO error when decoding.
   */
  public static ManifestFile decode(byte[] manifestData) throws IOException {
    return AvroEncoderUtil.decode(manifestData);
  }

  static ManifestReader<?> open(
      ManifestFile manifest, FileIO io, Map<Integer, PartitionSpec> specsById) {
    switch (manifest.content()) {
      case DATA:
        return ManifestFiles.read(manifest, io, specsById);
      case DELETES:
        return ManifestFiles.readDeleteManifest(manifest, io, specsById);
    }
    throw new UnsupportedOperationException(
        "Cannot read unknown manifest type: " + manifest.content());
  }

  static ManifestFile copyAppendManifest(
      int formatVersion,
      int specId,
      InputFile toCopy,
      Map<Integer, PartitionSpec> specsById,
      EncryptedOutputFile outputFile,
      long snapshotId,
      SnapshotSummary.Builder summaryBuilder) {
    // use metadata that will add the current snapshot's ID for the rewrite
    // read first_row_id as null because this copies the incoming manifest before commit
    InheritableMetadata inheritableMetadata = InheritableMetadataFactory.forCopy(snapshotId);
    try (ManifestReader<DataFile> reader =
        new ManifestReader<>(
            toCopy, specId, specsById, inheritableMetadata, null, FileType.DATA_FILES)) {
      return copyManifestInternal(

View on GitHub (pinned to 86d9c8fc54)

Solutions

1. Upgrade the Iceberg library to one that understands the manifest content type in the table
2. Verify the manifest list file was not produced/corrupted by external tooling
3. If integrating with custom code, map unknown content types explicitly instead of relying on the switch fallthrough

Example fix

// before
ManifestReader<?> reader = ManifestFiles.open(manifest, io, specsById);
// after
if (manifest.content() == null) {
  throw new IllegalArgumentException("Unknown manifest content, upgrade iceberg to read: " + manifest.location());
}
ManifestReader<?> reader = ManifestFiles.open(manifest, io, specsById);

if (manifest.content() != ManifestContent.DATA && manifest.content() != ManifestContent.DELETES) {
  throw new IllegalStateException("Unrecognized manifest content " + manifest.content() + "; upgrade iceberg");
}

boolean isOpenable(ManifestFile m) { return m.content() == ManifestContent.DATA || m.content() == ManifestContent.DELETES; }

try {
  reader = ManifestFiles.open(manifest, io, specsById);
} catch (UnsupportedOperationException e) {
  throw new IllegalStateException("Manifest content unknown to this client version: " + manifest.location(), e);
}

When it happens

Trigger: Calling ManifestFiles.open(manifest, io, specsById) where manifest.content() is not DATA or DELETES — typically a manifest whose content enum was written by a newer spec version or whose content field is missing/unparseable.

Common situations: Reading manifests written by a newer Iceberg version introducing a new content type; reading manifest list entries where the content field was dropped by forward-compatibility rules (unknown enum values become null in older clients).

Related errors

• Unsupported file content type: ${file.content()}
• Unsupported delete granularity: <granularity>
• Unknown delete file content:
• Cannot apply unknown unique constraint:
• %s doesn't implement copyWithStats

AI-assisted analysis of apache/iceberg@86d9c8fc54 (2026-09-12). Data as JSON: /api/errors/04bbf8917a4d05b7. Report an issue: GitHub.