apache/iceberg · error · UnsupportedOperationException

Unsupported table change: DropWatermark.

Error message

Unsupported table change: DropWatermark.

What it means

applySchemaChanges rejects TableChange.DropWatermark with UnsupportedOperationException; the Iceberg schema update machinery exposed through the Flink catalog cannot express watermark removal as a table change.

Source

Thrown at flink/v2.3/flink/src/main/java/org/apache/iceberg/flink/util/FlinkAlterTableUtil.java:139

   * @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();
    Preconditions.checkArgument(
        FlinkCompatibilityUtil.isPhysicalColumn(flinkColumn),

View on GitHub (pinned to 86d9c8fc54)

Solutions

1. Skip the DROP WATERMARK clause in migration scripts targeting Iceberg tables.
2. Manage watermarks in the Flink job/source definitions rather than table metadata.
3. Wrap the alter call and translate unsupported changes into no-ops only if your application semantics allow it.

if (changes.stream().anyMatch(c -> c instanceof TableChange.DropWatermark)) { throw new IllegalArgumentException('DROP WATERMARK is unsupported on Iceberg tables'); }

try { catalog.alterTable(tableIdent, changes); } catch (UnsupportedOperationException e) { LOG.info('Ignoring unsupported DROP WATERMARK for Iceberg table'); }

When it happens

Trigger: Executing 'ALTER TABLE ... DROP WATERMARK' against a table accessed via the Iceberg Flink catalog.

Common situations: Cleaning up DDL originally written for Flink's native catalogs and replaying it against Iceberg tables; automated migration scripts that include watermark clauses.

Related errors

• Unsupported table change: AddWatermark.
• Unsupported table change: ModifyWatermark.
• 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/9fdee5b40ea5238f. Report an issue: GitHub.