Logical Decoding Message Examples

NOTE: This project has been moved over to the Decodable examples repository and this repository is not maintained any longer.

Several examples demonstrating the usage of Postgres logical decoding messages, as emitted using the pg_logical_emit_message() function.

Requirements

Java 11
Docker

Build

Run the following command to build this project:

mvn clean verify

Pass the -Dquick option to skip all non-essential plug-ins and create the output artifact as quickly as possible:

mvn clean verify -Dquick

Run the following command to format the source code and organize the imports as per the project's conventions:

mvn process-sources

This code base is available under the Apache License, version 2.

Running the Examples

Start a Postgres database using the Docker Compose file in this directory:

docker compose up

Start a Postgres client session:

docker run --tty --rm -i \
    --network logical-decoding-network \
    quay.io/debezium/tooling:1.2 \
    bash -c 'pgcli postgresql://postgresuser:postgrespw@order-db:5432/orderdb'

Import the project into your IDE and run the main class dev.morling.demos.logicaldecoding.Main.

In the Postgres client sesion run:

CREATE TABLE data(id serial primary key, data text);

BEGIN;
SELECT * FROM pg_logical_emit_message(true, 'audit', '{ "user" : "John", "client_ip" : "192.168.1.1" }');
INSERT INTO data(data) VALUES('aaa');
INSERT INTO data(data) VALUES('bbb');
COMMIT;

In the logs of the main class observe how the cange events for the two rows in the data table are enriched with the audit metadata provided via pg_logical_emit_message() as part of the same transaction before.