apache/iceberg · error · UnsupportedOperationException

Unsupported split change: %s

Error message

Unsupported split change: %s

What it means

IcebergSourceSplitReader only supports SplitsAddition changes. If the SourceReader hands it any other SplitsChange subtype (e.g. SplitsRemoval), it throws UnsupportedOperationException naming the change class. This reflects that removals/redistribution are handled elsewhere in this reader implementation.

Source

Thrown at flink/v2.3/flink/src/main/java/org/apache/iceberg/flink/source/reader/IcebergSourceSplitReader.java:109

    }

    if (currentReader.hasNext()) {
      // Because Iterator#next() doesn't support checked exception,
      // we need to wrap and unwrap the checked IOException with UncheckedIOException
      try {
        return currentReader.next();
      } catch (UncheckedIOException e) {
        throw e.getCause();
      }
    } else {
      return finishSplit();
    }
  }

  @Override
  public void handleSplitsChanges(SplitsChange<IcebergSourceSplit> splitsChange) {
    if (!(splitsChange instanceof SplitsAddition)) {
      throw new UnsupportedOperationException(
          String.format("Unsupported split change: %s", splitsChange.getClass()));
    }

    if (splitComparator != null) {
      List<IcebergSourceSplit> newSplits = Lists.newArrayList(splitsChange.splits());
      newSplits.sort(splitComparator);
      LOG.info("Add {} splits to reader: {}", newSplits.size(), newSplits);
      splits.addAll(newSplits);
    } else {
      LOG.info("Add {} splits to reader", splitsChange.splits().size());
      splits.addAll(splitsChange.splits());
    }
    metrics.incrementAssignedSplits(splitsChange.splits().size());
    metrics.incrementAssignedBytes(calculateBytes(splitsChange));
  }

  @Override
  public void wakeUp() {

View on GitHub (pinned to 86d9c8fc54)

Solutions

1. Ensure the split enumerator only assigns new splits via SplitsAddition to this reader.
2. Remove/return splits at the enumerator level rather than sending SplitsRemoval to readers.
3. If you own a custom enumerator, filter out non-addition changes before assigning to IcebergSource readers.
4. Check Flink connector version compatibility; upgrade iceberg-flink runtime to match your Flink version.

Example fix

// before
reader.handleSplitsChanges(new SplitsRemoval<>(splits));
// after
// do not send removals to IcebergSourceSplitReader; handle in enumerator
// reader.handleSplitsChanges(new SplitsAddition<>(newSplits));

if (splitsChange instanceof SplitsAddition) { reader.handleSplitsChanges(splitsChange); } else { /* handle removal/redistribution in enumerator */ }

boolean isAddition(SplitsChange<IcebergSourceSplit> c) { return c instanceof SplitsAddition; }

try { reader.handleSplitsChanges(change); } catch (UnsupportedOperationException e) { LOG.warn('Non-addition split change rejected: {}', change.getClass()); }

When it happens

Trigger: The enumerator sends a SplitsChange other than SplitsAddition (such as SplitsRemoval) to the reader via handleSplitsChanges, typically during split assignment changes, scaling down of readers, or custom enumerator implementations.

Common situations: Custom SourceEnumerator implementations that issue removal changes; upgrading Flink connectors and the framework emitting removal events; state redistribution after rescaling a job.

Understand the failure class

Background: UnsupportedOperationException and "is not supported" errors: when a library deliberately refuses a call — this error's family across 30 libraries.

Related errors

• Unsupported split change: %s
• Unsupported split change: {splitsChange.getClass()}
• Unsupported split change: %s
• Altering schema is not supported in the old alterTable API.
• Altering partition keys is not supported yet.

AI-assisted analysis of apache/iceberg@86d9c8fc54 (2026-09-12). Data as JSON: /api/errors/c8a4a30827601321. Report an issue: GitHub.