{"record":{"id":"b93ec9e6f45ce3f1","repo":"apache/iceberg","slug":"unsupported-table-change-addwatermark","errorCode":null,"errorMessage":"Unsupported table change: AddWatermark.","messagePattern":"Unsupported table change: AddWatermark\\.","errorType":"exception","errorClass":"UnsupportedOperationException","httpStatus":null,"severity":"error","filePath":"flink/v1.20/flink/src/main/java/org/apache/iceberg/flink/util/FlinkAlterTableUtil.java","lineNumber":135,"sourceCode":"  /**\n   * Applies a list of Flink table changes to an {@link UpdateSchema} operation.\n   *\n   * @param pendingUpdate an uncommitted UpdateSchema operation to configure\n   * @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","sourceCodeStart":117,"sourceCodeEnd":153,"githubUrl":"https://github.com/apache/iceberg/blob/86d9c8fc543e7c56c9f624eb725f76c9baff9570/flink/v1.20/flink/src/main/java/org/apache/iceberg/flink/util/FlinkAlterTableUtil.java#L117-L153","documentation":"FlinkAlterTableUtil.applySchemaChanges translates Flink TableChange objects into Iceberg UpdateSchema operations. Watermark changes have no Iceberg schema representation, so AddWatermark is explicitly rejected with UnsupportedOperationException.","triggerScenarios":"Executing a Flink SQL `ALTER TABLE ... ADD WATERMARK` (or calling CatalogBaseTable change application) against an Iceberg catalog where the change list contains a TableChange.AddWatermark.","commonSituations":"Porting Flink SQL DDL written for other connectors (which support watermarks) to an Iceberg table; ORM/schema-sync tools generating watermark clauses.","solutions":["Remove the ADD WATERMARK clause from the DDL","Manage event-time/watermark semantics in the Flink job (e.g. via watermark strategy on the source) instead of the table schema","Apply other changes in a separate statement that excludes watermark changes"],"exampleFix":"// before\nALTER TABLE iceberg_table ADD WATERMARK FOR rowtime AS rowtime - INTERVAL '5' SECOND;\n// after\n// define WatermarkStrategy in the Flink source/job instead of the Iceberg table","handlingStrategy":"validation","validationCode":"if (changes.stream().anyMatch(c -> c instanceof TableChange.AddWatermark)) {\n  throw new IllegalArgumentException(\"Watermark changes are unsupported on Iceberg tables\");\n}","typeGuard":null,"tryCatchPattern":"try {\n  FlinkAlterTableUtil.applySchemaChanges(table, changes);\n} catch (UnsupportedOperationException e) {\n  // strip watermark changes and retry, or fail with a clear user message\n}","preventionTips":["Never emit watermark DDL for Iceberg-backed tables","Define watermark strategies in the Flink job, not the catalog","Filter TableChange lists by supported types before applying"],"tags":["flink","ddl","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"}