:page-aliases: configuration/decode-logical-decoding-message-content.adoc
[id="decode-logical-decoding-message-content"]
= Decode Logical Decoding Message Content

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The `DecodeLogicalDecodingMessageContent` SMT converts the binary content of a PostgreSQL logical decoding message to a structured form.
You can use the SMT on its own, or in conjunction with another SMT, such as the link:/documentation/reference/transformations/outbox-event-router[Outbox Event Router].

[[example-decode-logical-decoding-message-content]]
== Example

You configure a connector to use the `DecodeLogicalDecodingMessageContent` SMT by adding the SMT to the Kafka Connect configuration for the connector, as in the following example:

[source]
----
"connector.class": "io.debezium.connector.postgresql.PostgresConnector",
...
"transforms": "decodeLogicalDecodingMessageContent",
"transforms.decodeLogicalDecodingMessageContent.type": "io.debezium.connector.postgresql.transforms.DecodeLogicalDecodingMessageContent",
"key.converter": "org.apache.kafka.connect.json.JsonConverter",
"key.converter.schemas.enable": false,
"value.converter": "org.apache.kafka.connect.json.JsonConverter",
"value.converter.schemas.enable": "false",
...
----

The following example shows key and value of an event record before and after the transformation is applied.

.Effect of applying the `DecodeLogicalDecodingMessageContent` SMT
====
Key before the SMT processes the record::
+
[source,json]
----
{
	"prefix": "test-prefix"
}
----

Value before the SMT processes the record::
+
[source,json]
----
{
	"op": "m",
	"ts_ms": 1723115240065,
	"source": {
		"version": "3.0.0-SNAPSHOT",
		"connector": "postgresql",
		"name": "connector-name",
		"ts_ms": 1723115239782,
		"snapshot": "false",
		"db": "source-db",
		"sequence": "[\"26997744\",\"26997904\"]",
		"ts_us": 1723115239782690,
		"ts_ns": 1723115239782690000,
		"schema": "",
		"table": "",
		"txId": 756,
		"lsn": 26997904,
		"xmin": null
	},
	"message": {
		"prefix": "test-prefix",
		"content": "eyJpZCI6IDEsICJpdGVtIjogIkRlYmV6aXVtIGluIEFjdGlvbiIsICJzdGF0dXMiOiAiRU5URVJFRCIsICJxdWFudGl0eSI6IDIsICJ0b3RhbFByaWNlIjogMzkuOTh9"
	}
}
----

Key after the SMT processes the record:: null

Value after the SMT processes the record::
+
[source,json]
----
{
	"op": "c",
	"ts_ms": 1723115415729,
	"source": {
		"version": "3.0.0-SNAPSHOT",
		"connector": "postgresql",
		"name": "connector-name",
		"ts_ms": 1723115415640,
		"snapshot": "false",
		"db": "source-db",
		"sequence": "[\"26717416\",\"26717576\"]",
		"ts_us": 1723115415640161,
		"ts_ns": 1723115415640161000,
		"schema": "",
		"table": "",
		"txId": 745,
		"lsn": 26717576,
		"xmin": null
	},
	"after": {
		"id": 1,
		"item": "Debezium in Action",
		"status": "ENTERED",
		"quantity": 2,
		"totalPrice": 39.98
	}
}
----

In the preceding example, the SMT applies the following changes to the original event record:

. Removes the key that contained the `prefix` field in the original logical decoding message (`"prefix": "test-prefix"`)
. Converts the value of the `op` field from an `m` (message) to a `c` (create), effectively changing the type of the event from a message to an `INSERT`.
. Replaces the `message` field with an `after` field that contains the decoded content of a logical decoding message.


After the SMT applies these changes, the record can be more easily processed by other SMTs, such as the Outbox Event Router.

====

[[decode-logical-decoding-message-content-configuration-options]]
== Configuration options

The following table lists the configuration options that you can use with the `DecodeLogicalDecodingMessageContent` SMT.

.`DecodeLogicalDecodingMessageContent` SMT configuration options
[cols="15%a,10%a,10%a,65%a"]
|===
|Property
|Type
|Default
|Description

|[[decode-logical-decoding-message-content-fields-null-include]]<<decode-logical-decoding-message-content-fields-null-include, `fields.null.include`>>
|boolean
|false
|Specifies how the decoding process handles fields that have null values in the source message.
By default, the transformation removes fields that have null values.
|===