Change data capture (CDC) is a data integration pattern to track changes in a database so that actions can be taken using the changed data. Debezium is probably the most popular open source platform for CDC. Originally providing Kafka source connectors, it also supports a ready-to-use application called Debezium server. The standalone application can be used to stream change events to other messaging infrastructure such as Google Cloud Pub/Sub, Amazon Kinesis and Apache Pulsar. In this post, we develop a CDC solution locally using Docker. The source of the theLook eCommerce is modified to generate data continuously, and the data is inserted into multiple tables of a PostgreSQL database. Among those tables, two of them are tracked by the Debezium server, and it pushes row-level changes of those tables into Pub/Sub topics on the Pub/Sub emulator. Finally, messages of the topics are read by a Python application.

In Part 3, we developed a dbt project that targets Google BigQuery with fictional pizza shop data. Two dimension tables that keep product and user records are created as Type 2 slowly changing dimension (SCD Type 2) tables, and one transactional fact table is built to keep pizza orders. The fact table is denormalized using nested and repeated fields for improving query performance. In this post, we discuss how to set up an ETL process on the project using Apache Airflow.

In this series, we discuss practical examples of data warehouse and lakehouse development where data transformation is performed by the data build tool (dbt) and ETL is managed by Apache Airflow. In Part 1, we developed a dbt project on PostgreSQL using fictional pizza shop data. At the end, the data sets are modelled by two SCD type 2 dimension tables and one transactional fact table. In this post, we create a new dbt project that targets Google BigQuery. While the dimension tables are kept by the same SCD type 2 approach, the fact table is denormalized using nested and repeated fields, which potentially can improve query performance by pre-joining corresponding dimension records.