{"record":{"id":"dab471d07b050914","repo":"apache/iceberg","slug":"unsupported-table-change-dropconstraint-dab471","errorCode":null,"errorMessage":"Unsupported table change: DropConstraint.","messagePattern":"Unsupported table change: DropConstraint\\.","errorType":"exception","errorClass":"UnsupportedOperationException","httpStatus":null,"severity":"error","filePath":"flink/v2.1/flink/src/main/java/org/apache/iceberg/flink/util/FlinkAlterTableUtil.java","lineNumber":147,"sourceCode":"        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),\n        \"Unsupported table change: Adding computed column %s.\",\n        flinkColumn.getName());\n\n    Type icebergType = FlinkSchemaUtil.convert(flinkColumn.getDataType().getLogicalType());\n\n    if (flinkColumn.getDataType().getLogicalType().isNullable()) {\n      pendingUpdate.addColumn(\n          flinkColumn.getName(), icebergType, flinkColumn.getComment().orElse(null));","sourceCodeStart":129,"sourceCodeEnd":165,"githubUrl":"https://github.com/apache/iceberg/blob/86d9c8fc543e7c56c9f624eb725f76c9baff9570/flink/v2.1/flink/src/main/java/org/apache/iceberg/flink/util/FlinkAlterTableUtil.java#L129-L165","documentation":"FlinkAlterTableUtil.applySchemaChanges does not implement TableChange.DropConstraint, so dropping a constraint through the Flink catalog raises UnsupportedOperationException. Iceberg currently supports setting identifier fields (primary key) but no generic constraint drop.","triggerScenarios":"Running 'ALTER TABLE ... DROP PRIMARY KEY/CONSTRAINT <name>' via Flink SQL on an Iceberg table.","commonSituations":"Trying to remove an identifier-field (primary key) definition from an Iceberg table through Flink DDL.","solutions":["Clear identifier fields via Iceberg API directly: updateSchema().setIdentifierFields(\"\") / rename the identifier field set instead of DROP CONSTRAINT","Drop and recreate the table without the primary key if the identifier fields must be removed","Perform the change with a Spark/Java UpdateSchema against the same table"],"exampleFix":"// before (flink sql)\nALTER TABLE iceberg_table DROP PRIMARY KEY;\n// after (java)\ntable.updateSchema().setIdentifierFields(\"\").commit();","handlingStrategy":"try-catch","validationCode":"if (changes.stream().anyMatch(c -> c instanceof TableChange.DropConstraint)) {\n  throw new IllegalArgumentException(\"DROP CONSTRAINT is not supported; clear identifier fields via UpdateSchema\");\n}","typeGuard":null,"tryCatchPattern":"try {\n  FlinkAlterTableUtil.applySchemaChanges(update, changes);\n} catch (UnsupportedOperationException e) {\n  if (e.getMessage().contains(\"DropConstraint\")) { /* fall back to updateSchema().setIdentifierFields(\"\") */ }\n  throw e;\n}","preventionTips":["Use UpdateSchema.setIdentifierFields(\"\") (or field names) to manage primary keys instead of DROP CONSTRAINT DDL","Avoid generic constraint DDL scripts on Iceberg tables"],"tags":["flink","schema-change","constraint","unsupported"],"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"}