How to map Java and SQL arrays with JPA and Hibernate

Introduction Hibernate custom Types allow you to map all sorts of database specific column types, like IP address, JSON columns, bit sets or SQL arrays. There are two ways to define a custom Hibernate Type: the UserType interface Java and SQL descriptors The latter option is preferred since it allows you to better split the Java-to-JDBC and the JDBC-to-SQL type handling. In this article, we are going to see how you can map SQL arrays to their Java counterpart.

The best way to soft delete with Hibernate

Introduction Each database application is unique. While most of the time, deleting a record is the best approach, there are times when the application requirements demand that database records should never be physically deleted. So who uses this technique? For instance, StackOverflow does it for all Posts (e.g. Questions and Answers). The StackOverflow Posts table has a ClosedDate column which acts as a soft delete mechanism since it hides an Answer for all users who have less than 10k reputation. If you’re using Oracle, you can take advantage of its Flashback capabilities,… Read More

How does a relational database work

Introduction While doing my High-Performance Java Persistence training, I came to realize that it’s worth explaining how a relational database works, as otherwise, it is very difficult to grasp many transaction-related concepts like atomicity, durability, and checkpoints. In this post, I’m going to give a high-level explanation of how a relational database works internally while also hinting some database-specific implementation details.

Book Review – SQL Antipatterns

Introduction I’ve just finished the wonderful SQL Antipatterns book by Bill Karwin. The book is a must-have reference for any developer that has to interact with a relational database system. This post is a review of what this book is all about and why you should be interested in reading it.

How to map table rows to columns using SQL PIVOT or CASE expressions

Introduction I’m now reading the wonderful SQL Antipatterns book by Bill Karwin. The book is a great reference for any developer that needs to interact with a Relational Database System. In this book, the Entity-Attribute-Value (EAV) model is portrayed as an Anti-Pattern. Although I must admit that a proper relational schema is almost always the best approach when designing an enterprise system, there are use cases when the EAV model is justified. In this post, I’m going to explain when to use EAV and how to transpose a ResultSet so that rows… Read More