{"record":{"id":"9fdee5b40ea5238f","repo":"apache/iceberg","slug":"unsupported-table-change-dropwatermark-9fdee5","errorCode":null,"errorMessage":"Unsupported table change: DropWatermark.","messagePattern":"Unsupported table change: DropWatermark\\.","errorType":"exception","errorClass":"UnsupportedOperationException","httpStatus":null,"severity":"error","filePath":"flink/v2.3/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/v2.3/flink/src/main/java/org/apache/iceberg/flink/util/FlinkAlterTableUtil.java#L121-L157","documentation":"applySchemaChanges rejects TableChange.DropWatermark with UnsupportedOperationException; the Iceberg schema update machinery exposed through the Flink catalog cannot express watermark removal as a table change.","triggerScenarios":"Executing 'ALTER TABLE ... DROP WATERMARK' against a table accessed via the Iceberg Flink catalog.","commonSituations":"Cleaning up DDL originally written for Flink's native catalogs and replaying it against Iceberg tables; automated migration scripts that include watermark clauses.","solutions":["Skip the DROP WATERMARK clause in migration scripts targeting Iceberg tables.","Manage watermarks in the Flink job/source definitions rather than table metadata.","Wrap the alter call and translate unsupported changes into no-ops only if your application semantics allow it."],"exampleFix":null,"handlingStrategy":"validation","validationCode":"if (changes.stream().anyMatch(c -> c instanceof TableChange.DropWatermark)) { throw new IllegalArgumentException('DROP WATERMARK is unsupported on Iceberg tables'); }","typeGuard":null,"tryCatchPattern":"try { catalog.alterTable(tableIdent, changes); } catch (UnsupportedOperationException e) { LOG.info('Ignoring unsupported DROP WATERMARK for Iceberg table'); }","preventionTips":["Exclude watermark changes from automated DDL migrations to Iceberg","Keep watermark semantics in Flink pipeline definitions","Handle unsupported changes explicitly rather than blanket-retrying"],"tags":["flink","sql","schema-change","unsupported"],"backgroundTag":"operation-not-supported","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"}