anchor.diff:  
   The {prodname} MySQL connector generates a data change event for each row-level `INSERT`, `UPDATE`, and `DELETE` operation. Each event contains a key and a value. The structure of the key and the value depends on the table that was changed. 
   
  -{prodname} and Kafka Connect are designed around _continuous streams of event messages_. However, the structure of these events may change over time, which can be difficult for consumers to handle. To address this, each event contains the schema for its content, which makes each event self-contained. The following skeleton JSON shows the basic structure of a change event: 
  +{prodname} and Kafka Connect are designed around _continuous streams of event messages_. However, the structure of these events may change over time, which can be difficult for consumers to handle. To address this, each event contains the schema for its content or, if you are using a schema registry, a schema ID that a consumer can use to obtain the schema from the registry. This makes each event self-contained. 
  +
  +The following skeleton JSON shows the basic four parts of a change event. However, how you configure the Kafka Connect converter that you choose to use in your application determines the representation of these four parts in change events. A `schema` field is in a change event only when you configure the converter to produce it. Likewise, the event key and event payload are in a change event only if you configure a converter to produce it. If you use the JSON converver and you configure it to produce all four basic change event parts, change events have this structure: 
   
   [source,json,index=0]
   ----
  
positive.code: 
  |8
  |`source`
  a| Mandatory field that describes the source metadata for the event. The `source` structure shows information about MySQL’s record of this change, which provides traceability. It also has information you can use to compare to other events in this and other topics to know whether this event occurred before, after, or as part of the same MySQL commit as other events. The source metadata includes: 
  
  * {prodname} version
  * Connector name
  
negative.code: === Primary key updates
  
  An `UPDATE` operation that changes a row's primary key field(s) is known
  as a primary key change. For a primary key change, in place an `UPDATE` event record, the connector emits a `DELETE` event record for the old key and a `CREATE` event record for the new (updated) key. These events have the usual structure and content, and in addition, each one has a message header related to the primary key change: 
  
  * The `DELETE` event record has `__debezium.newkey` as a message header. The value of this header is the new primary key for the updated row.
  
  