# Kafka Connect ExtractChangedRecordState (Debezium) SMT Usage Reference for Confluent Cloud The `ExtractChangedRecordState` SMT (`io.debezium.transforms.ExtractChangedRecordState`) inspects Debezium change events and attaches Apache Kafka® message headers identifying modified and unmodified fields during database `UPDATE` operations. ## Description Use this SMT for downstream consumers to detect field-level changes without comparing the full `before` and `after` structures. * For an `UPDATE` event, the SMT compares the `before` and `after` field values to populate the headers. * For `INSERT`, `DELETE`, and read or snapshot events generated when Debezium performs its initial data snapshot, the SMT adds the headers configured through `header.changed.name` and `header.unchanged.name` as empty lists. For complete details, see the official Debezium [ExtractChangedRecordState SMT](https://debezium.io/documentation/reference/stable/transformations/event-changes.html) documentation. For the full list of available SMTs, see [Kafka Connect Single Message Transformation Reference for Confluent Cloud](overview.md#connect-transforms-supported). ## Limitations The `ExtractChangedRecordState` SMT is available only for managed Debezium change data capture (CDC) Source connectors, such as PostgreSQL, MySQL, SQL Server, and MariaDB, and the Oracle XStream CDC Source connector. Field-level change detection applies to `UPDATE` events only. ## Properties To add headers, set `header.changed.name`, `header.unchanged.name`, or both. The following table lists the configuration options for the `ExtractChangedRecordState` SMT. | Name | Description | Type | Importance | |-------------------------|-------------------------------------------------------------------------------------------------------------------------------------------------|--------|--------------| | `header.changed.name` | The name of the Kafka message header that stores a comma-separated
list of the fields the database operation changed. | string | low | | `header.unchanged.name` | The name of the Kafka message header that stores a comma-separated
list of the fields that remained unchanged after the database operation. | string | low | ## Example The following example adds a `Changed` header and an `Unchanged` header to each record. ```json "transforms": "changes", "transforms.changes.type": "io.debezium.transforms.ExtractChangedRecordState", "transforms.changes.header.changed.name": "Changed", "transforms.changes.header.unchanged.name": "Unchanged" ``` #### NOTE This SMT adds its output to the record headers, not to the record value. ## Predicates Transformations can be configured with *predicates* so that the transformation is applied only to records which satisfy a condition. You can use predicates in a transformation chain and, when combined with the [Kafka Connect Filter (Kafka) SMT Usage Reference for Confluent Cloud](filter-ak.md#ak-filter), predicates can conditionally filter out specific records. For details and examples, see [Predicates](filter-ak.md#predicates).