apache/iceberg · error · IllegalArgumentException

Unsupported changelog scan task type:

Error message

Unsupported changelog scan task type: 

What it means

ChangelogRowReader.openChangelogScanTask dispatches on the ChangelogScanTask subtype and throws IllegalArgumentException when the task type is none of AddedRowsScanTask, DeletedRowsScanTask, or DeletedDataFileScanTask. This guards against unknown/future task types produced by a mismatched scan planner.

Source

Thrown at spark/v4.1/spark/src/main/java/org/apache/iceberg/spark/source/ChangelogRowReader.java:110

    metadataRow.update(0, UTF8String.fromString(task.operation().name()));
    metadataRow.update(1, task.changeOrdinal());
    metadataRow.update(2, task.commitSnapshotId());

    return metadataRow;
  }

  private CloseableIterable<InternalRow> openChangelogScanTask(ChangelogScanTask task) {
    if (task instanceof AddedRowsScanTask) {
      return openAddedRowsScanTask((AddedRowsScanTask) task);

    } else if (task instanceof DeletedRowsScanTask) {
      throw new UnsupportedOperationException("Deleted rows scan task is not supported yet");

    } else if (task instanceof DeletedDataFileScanTask) {
      return openDeletedDataFileScanTask((DeletedDataFileScanTask) task);

    } else {
      throw new IllegalArgumentException(
          "Unsupported changelog scan task type: " + task.getClass().getName());
    }
  }

  CloseableIterable<InternalRow> openAddedRowsScanTask(AddedRowsScanTask task) {
    String filePath = task.file().location();
    SparkDeleteFilter deletes = new SparkDeleteFilter(filePath, task.deletes(), counter(), true);
    return deletes.filter(rows(task, deletes.requiredSchema()));
  }

  private CloseableIterable<InternalRow> openDeletedDataFileScanTask(DeletedDataFileScanTask task) {
    String filePath = task.file().location();
    SparkDeleteFilter deletes =
        new SparkDeleteFilter(filePath, task.existingDeletes(), counter(), true);
    return deletes.filter(rows(task, deletes.requiredSchema()));
  }

  private CloseableIterable<InternalRow> rows(ContentScanTask<DataFile> task, Schema readSchema) {

View on GitHub (pinned to 86d9c8fc54)

Solutions

1. Align all Iceberg module versions (spark runtime + core) to the same release
2. Check which task class name is printed in the message and whether it comes from a custom/old jar
3. Remove duplicate/shaded Iceberg jars from the classpath
4. Upgrade iceberg-spark to a release that supports the task type

Example fix

// before: mixed iceberg-core 1.6 with iceberg-spark 1.4 on classpath
// after: use one version
implementation 'org.apache.iceberg:iceberg-spark-runtime-4.1_2.13:1.6.1'

// before reading changelog tasks
if (!(task instanceof AddedRowsScanTask) && !(task instanceof DeletedRowsScanTask) && !(task instanceof DeletedDataFileScanTask)) {
  throw new IllegalStateException("Unsupported changelog task: " + task.getClass().getName());
}

boolean isSupportedChangelogTask(ChangelogScanTask t) {
  return t instanceof AddedRowsScanTask || t instanceof DeletedRowsScanTask || t instanceof DeletedDataFileScanTask;
}

try { reader.openChangelogScanTask(task); } catch (IllegalArgumentException e) { /* inspect task class, fix jar versions */ }

When it happens

Trigger: A ChangelogScanTask subclass not handled by the if/else chain reaches openChangelogScanTask, e.g. a new task type added in a newer Iceberg core while this Spark reader is older, or a custom scan task implementation.

Common situations: Version skew between iceberg-spark and iceberg-core jars on the classpath (mixed versions after upgrade); custom ChangelogScanTask implementations; internal bugs in scan planning.

Understand the failure class

Background: Invalid enum value errors: "Unknown type", "Invalid scope", "must be one of" — when a string is not on the library's allowed list — this error's family across 23 libraries.

Related errors

• Unsupported manifest content type:${content}
• Cannot pass path based identifier to %s method. %s is a path
• Unsupported command: ${command}
• Unknown time travel: ${timeTravel}
• Unsupported Spark view dependency: ${dependency.getClass().g

AI-assisted analysis of apache/iceberg@86d9c8fc54 (2026-09-12). Data as JSON: /api/errors/4ac4f613f768332e. Report an issue: GitHub.