apache/iceberg · error · UnsupportedOperationException

Unsupported table change: ModifyWatermark.

Error message

Unsupported table change: ModifyWatermark.

What it means

applySchemaChanges rejects watermark modifications: any TableChange.ModifyWatermark reaching the Iceberg catalog alter path throws UnsupportedOperationException because Iceberg (via this Flink bridge) cannot store watermark table properties.

Source

Thrown at flink/v2.3/flink/src/main/java/org/apache/iceberg/flink/util/FlinkAlterTableUtil.java:137

   *
   * @param pendingUpdate an uncommitted UpdateSchema operation to configure
   * @param schemaChanges a list of Flink table changes
   */
  public static void applySchemaChanges(
      UpdateSchema pendingUpdate, List<TableChange> schemaChanges) {
    for (TableChange change : schemaChanges) {
      if (change instanceof TableChange.AddColumn) {
        applyAddColumn(pendingUpdate, (TableChange.AddColumn) change);
      } else if (change instanceof TableChange.ModifyColumn) {
        TableChange.ModifyColumn modifyColumn = (TableChange.ModifyColumn) change;
        applyModifyColumn(pendingUpdate, modifyColumn);
      } else if (change instanceof TableChange.DropColumn) {
        TableChange.DropColumn dropColumn = (TableChange.DropColumn) change;
        pendingUpdate.deleteColumn(dropColumn.getColumnName());
      } else if (change instanceof TableChange.AddWatermark) {
        throw new UnsupportedOperationException("Unsupported table change: AddWatermark.");
      } else if (change instanceof TableChange.ModifyWatermark) {
        throw new UnsupportedOperationException("Unsupported table change: ModifyWatermark.");
      } else if (change instanceof TableChange.DropWatermark) {
        throw new UnsupportedOperationException("Unsupported table change: DropWatermark.");
      } else if (change instanceof TableChange.AddUniqueConstraint) {
        TableChange.AddUniqueConstraint addPk = (TableChange.AddUniqueConstraint) change;
        applyUniqueConstraint(pendingUpdate, addPk.getConstraint());
      } else if (change instanceof TableChange.ModifyUniqueConstraint) {
        TableChange.ModifyUniqueConstraint modifyPk = (TableChange.ModifyUniqueConstraint) change;
        applyUniqueConstraint(pendingUpdate, modifyPk.getNewConstraint());
      } else if (change instanceof TableChange.DropConstraint) {
        throw new UnsupportedOperationException("Unsupported table change: DropConstraint.");
      } else {
        throw new UnsupportedOperationException("Cannot apply unknown table change: " + change);
      }
    }
  }

  private static void applyAddColumn(UpdateSchema pendingUpdate, TableChange.AddColumn addColumn) {
    Column flinkColumn = addColumn.getColumn();

View on GitHub (pinned to 86d9c8fc54)

Solutions

1. Remove the MODIFY WATERMARK statement; redefine the watermark in the consuming Flink job/source DDL instead.
2. Drop and recreate the view/source definition with the desired watermark semantics outside Iceberg metadata.
3. Check Iceberg release notes for watermark table-feature support before retrying.

boolean hasWatermarkChange = changes.stream().anyMatch(c -> c instanceof TableChange.ModifyWatermark || c instanceof TableChange.AddWatermark || c instanceof TableChange.DropWatermark);
if (hasWatermarkChange) throw new IllegalArgumentException('Watermark changes unsupported by Iceberg Flink catalog');

try { catalog.alterTable(tableIdent, changes); } catch (UnsupportedOperationException e) { /* fall back to pipeline-level watermark config */ }

When it happens

Trigger: Executing 'ALTER TABLE ... MODIFY WATERMARK' (or ALTER ... REPLACE/WATERMARK adjustments) through the Iceberg Flink catalog.

Common situations: Migrating native Flink table DDL workflows to Iceberg tables and reusing watermark DDL statements unchanged.

Related errors

• Unsupported table change: AddWatermark.
• Unsupported table change: DropWatermark.
• Unsupported table change: DropConstraint.
• Unsupported table change: AddWatermark.
• Unsupported table change: ModifyWatermark.

AI-assisted analysis of apache/iceberg@86d9c8fc54 (2026-09-12). Data as JSON: /api/errors/0481272ec0a2d39e. Report an issue: GitHub.