diff --git a/ticdc/ticdc-avro-protocol.md b/ticdc/ticdc-avro-protocol.md index 4410b37becea9..46a816fd2207e 100644 --- a/ticdc/ticdc-avro-protocol.md +++ b/ticdc/ticdc-avro-protocol.md @@ -83,6 +83,8 @@ The data format of Value is the same as that of Key, by default. However, `field > - For Delete events, Avro only encodes the Key part. The Value part is empty. > - For Insert events, Avro encodes all column data to the Value part. > - For Update events, Avro encodes only all column data that is updated to the Value part. +> +> The Avro protocol does not encode the old values for Update and Delete events. Additionally, to be compatible with most Confluent sink connectors that rely on `null` records to identify deletions (`delete.on.null`), Delete events do not include extension information, such as `_tidb_commit_ts`, even when `enable-tidb-extension` is enabled. If you need these features, consider using other protocols such as Canal-JSON or Debezium. ## TiDB extension fields