{"record":{"id":"5244b128a01366bc","repo":"apache/iceberg","slug":"unsupported-table-change-dropwatermark-5244b1","errorCode":null,"errorMessage":"Unsupported table change: DropWatermark.","messagePattern":"Unsupported table change: DropWatermark\\.","errorType":"exception","errorClass":"UnsupportedOperationException","httpStatus":null,"severity":"error","filePath":"flink/v2.2/flink/src/main/java/org/apache/iceberg/flink/util/FlinkAlterTableUtil.java","lineNumber":139,"sourceCode":"   * @param schemaChanges a list of Flink table changes\n   */\n  public static void applySchemaChanges(\n      UpdateSchema pendingUpdate, List<TableChange> schemaChanges) {\n    for (TableChange change : schemaChanges) {\n      if (change instanceof TableChange.AddColumn) {\n        applyAddColumn(pendingUpdate, (TableChange.AddColumn) change);\n      } else if (change instanceof TableChange.ModifyColumn) {\n        TableChange.ModifyColumn modifyColumn = (TableChange.ModifyColumn) change;\n        applyModifyColumn(pendingUpdate, modifyColumn);\n      } else if (change instanceof TableChange.DropColumn) {\n        TableChange.DropColumn dropColumn = (TableChange.DropColumn) change;\n        pendingUpdate.deleteColumn(dropColumn.getColumnName());\n      } else if (change instanceof TableChange.AddWatermark) {\n        throw new UnsupportedOperationException(\"Unsupported table change: AddWatermark.\");\n      } else if (change instanceof TableChange.ModifyWatermark) {\n        throw new UnsupportedOperationException(\"Unsupported table change: ModifyWatermark.\");\n      } else if (change instanceof TableChange.DropWatermark) {\n        throw new UnsupportedOperationException(\"Unsupported table change: DropWatermark.\");\n      } else if (change instanceof TableChange.AddUniqueConstraint) {\n        TableChange.AddUniqueConstraint addPk = (TableChange.AddUniqueConstraint) change;\n        applyUniqueConstraint(pendingUpdate, addPk.getConstraint());\n      } else if (change instanceof TableChange.ModifyUniqueConstraint) {\n        TableChange.ModifyUniqueConstraint modifyPk = (TableChange.ModifyUniqueConstraint) change;\n        applyUniqueConstraint(pendingUpdate, modifyPk.getNewConstraint());\n      } else if (change instanceof TableChange.DropConstraint) {\n        throw new UnsupportedOperationException(\"Unsupported table change: DropConstraint.\");\n      } else {\n        throw new UnsupportedOperationException(\"Cannot apply unknown table change: \" + change);\n      }\n    }\n  }\n\n  private static void applyAddColumn(UpdateSchema pendingUpdate, TableChange.AddColumn addColumn) {\n    Column flinkColumn = addColumn.getColumn();\n    Preconditions.checkArgument(\n        FlinkCompatibilityUtil.isPhysicalColumn(flinkColumn),","sourceCodeStart":121,"sourceCodeEnd":157,"githubUrl":"https://github.com/apache/iceberg/blob/86d9c8fc543e7c56c9f624eb725f76c9baff9570/flink/v2.2/flink/src/main/java/org/apache/iceberg/flink/util/FlinkAlterTableUtil.java#L121-L157","documentation":"Guard in FlinkAlterTableUtil.applySchemaChanges: a DropWatermark change reached the Flink-to-Iceberg schema translation. Iceberg has no watermark concept in its schema, so the change is rejected rather than dropped silently.","triggerScenarios":"Executing 'ALTER TABLE ... DROP WATERMARK' (or applying a TableChange.DropWatermark) against an Iceberg table through the Flink catalog.","commonSituations":"Cleanup DDL scripts shared across table types hitting Iceberg tables; schema-sync tooling attempting to drop watermarks.","solutions":["Remove the DROP WATERMARK statement for Iceberg tables — there is no stored watermark to drop","Filter out watermark changes before passing TableChange objects to Iceberg DDL execution","Update schema-sync tooling to skip watermark operations for Iceberg catalogs"],"exampleFix":"// before\nchanges.add(TableChange.dropWatermark());\ntable.updateSchema(); // via applySchemaChanges -> throws\n// after\nList<TableChange> icebergChanges = changes.stream()\n    .filter(c -> !(c instanceof TableChange.DropWatermark))\n    .collect(Collectors.toList());","handlingStrategy":"validation","validationCode":"boolean hasDropWatermark = java.util.Arrays.stream(changes)\n    .anyMatch(c -> c instanceof TableChange.DropWatermark);\nif (hasDropWatermark) {\n  throw new IllegalArgumentException(\"Nothing to drop: Iceberg tables never store watermarks\");\n}","typeGuard":null,"tryCatchPattern":"try {\n  FlinkAlterTableUtil.applySchemaChanges(update, changes);\n} catch (UnsupportedOperationException e) {\n  LOG.warn(\"DROP WATERMARK is a no-op for Iceberg and was skipped: {}\", e.getMessage());\n}","preventionTips":["Skip DROP WATERMARK statements when the target is an Iceberg catalog","Write DDL migrations per-connector instead of sharing one script","Sanitize TableChange lists before applying schema updates to Iceberg"],"tags":["flink","ddl","unsupported-operation","watermark"],"backgroundTag":"unsupported-operation","analyzedSha":"86d9c8fc543e7c56c9f624eb725f76c9baff9570","analyzedAt":"2026-09-12T00:46:39.097Z","contentChangedAt":"2026-09-12T00:46:39.097Z","schemaVersion":2},"datasetVersion":"2026-09-14T16:17:12.679Z"}