{"record":{"id":"a9a683efe4b68de1","repo":"apache/iceberg","slug":"unsupported-table-change-dropwatermark","errorCode":null,"errorMessage":"Unsupported table change: DropWatermark.","messagePattern":"Unsupported table change: DropWatermark\\.","errorType":"exception","errorClass":"UnsupportedOperationException","httpStatus":null,"severity":"error","filePath":"flink/v1.20/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/v1.20/flink/src/main/java/org/apache/iceberg/flink/util/FlinkAlterTableUtil.java#L121-L157","documentation":"Guard in FlinkAlterTableUtil.applySchemaChanges: a DropWatermark table change was received. Since Iceberg schemas have no watermark concept, there is nothing to drop and the change is rejected rather than silently ignored.","triggerScenarios":"Executing `ALTER TABLE ... DROP WATERMARK` against an Iceberg-backed Flink table.","commonSituations":"Cleaning up Flink-specific DDL when switching a table from a Flink-native catalog to Iceberg; schema-sync tooling replaying full table definitions.","solutions":["Remove the DROP WATERMARK clause from the statement","Skip watermark changes entirely when migrating to Iceberg (they are implicitly absent)","Filter the TableChange list before calling applySchemaChanges"],"exampleFix":null,"handlingStrategy":"validation","validationCode":"if (changes.stream().anyMatch(c -> c instanceof TableChange.DropWatermark)) {\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  // ignore or log: watermark is implicitly absent in Iceberg\n}","preventionTips":["Skip watermark DDL when migrating from Flink-native to Iceberg catalogs","Pre-filter changes to supported TableChange types","Treat watermark operations as no-ops for Iceberg"],"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"}