Vlad Mihalcea

A beginner’s guide to database table relationships

Imagine having a tool that can automatically detect if you are using JPA and Hibernate properly. Hypersistence Optimizer is that tool!

Introduction

In a relational database, a relationship is formed by correlating rows belonging to different tables. A table relationship is established when a child table defines a Foreign Key column that references the Primary Key column of its parent table.

Every database table relationship is, therefore, built on top of Foreign Key columns, and there can be three table relationship types:

  • one-to-many is the most common relationship, and it associates a row from a parent table to multiple rows in a child table.
  • one-to-one requires the child table Primary Key to be associated via a Foreign Key with the parent table Primary Key column.
  • many-to-many requires a link table containing two Foreign Key columns that reference the two different parent tables.

In this article, we are going to describe all these three table relationships as well as their use cases.

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How to implement a database job queue using SKIP LOCKED

Imagine having a tool that can automatically detect if you are using JPA and Hibernate properly. Hypersistence Optimizer is that tool!

Introduction

In this article, we are going to see how we can implement a database job queue using SKIP LOCKED.

I decided to write this article while answering this Stack Overflow question asked by Rafael Winterhalter.

Since SKIP LOCKED is a lesser-known SQL feature, it’s a good opportunity to show you how to use it and why you should employ it, especially when implementing a job queue task.

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How to change the @OneToOne shared primary key column name with JPA and Hibernate

Imagine having a tool that can automatically detect if you are using JPA and Hibernate properly. Hypersistence Optimizer is that tool!

Introduction

In this article, we are going to see how you can change the @OneToOne shared primary key column name when using JPA and Hibernate. This has been a recurrent theme when answering questions about Hibernate or during my High-Performance Java Persistence training.

As previously explained, the one-to-one database table relationship requires the Primary Key to be shared among the parent and the child tables.

Unfortunately, just adding the JPA @OneToOne annotation in the child entity does not render a true one-to-one table relationship since a separate Foreign Key column will be used. Only when adding the @MapsId annotation will the JPA one-to-one association map to a real one-to-one table relationship.

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How does a relational database execute SQL statements and prepared statements

Imagine having a tool that can automatically detect if you are using JPA and Hibernate properly. Hypersistence Optimizer is that tool!

Introduction

In this article, we are going to see how a relational database executes SQL statements and prepared statements.

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Hypersistence Optimizer initial release

Imagine having a tool that can automatically detect if you are using JPA and Hibernate properly. Hypersistence Optimizer is that tool!

Introduction

At the end of 2018, I got this idea of writing a tool which can automatically detect JPA and Hibernate issues by scanning your data access layer and provide you optimization tips.

At the beginning of February, Thodoris Chaikalis surprised me with this Facebook comment which reinforced the idea that having such a tool would be really awesome for Java developers working with JPA and Hibernate.

Facebook Comment about a tool like Hypersistence Optimizer

At the end of February, I got some time off, and I started working on it, and the reaction on social media exceeded my expectations:

Today, I’m happy to announce to you that the initial version is ready.

Hypersistence Optimizer has finally arrived!

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Why you should avoid EXTRA Lazy Collections with Hibernate

Imagine having a tool that can automatically detect if you are using JPA and Hibernate properly. Hypersistence Optimizer is that tool!

Introduction

In this article, you are going to learn why using EXTRA Lazy Collections with Hibernate is a bad idea since it can lead to N+1 query issues and cause performance problems.

The reason I wanted to write this article is that I keep seeing it mentioned in StackOverflow or the Hibernate forum.

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How does the entity version property work when using JPA and Hibernate

Imagine having a tool that can automatically detect if you are using JPA and Hibernate properly. Hypersistence Optimizer is that tool!

Introduction

In this article, I’m going to show you how the JPA @Version entity property works when using Hibernate.

The most significant benefit of adding a version property to a JPA entity is that we can prevent the lost update anomaly, therefore ensuring that data integrity is not compromised.

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How do JPA persist, merge and Hibernate save, update, saveOrUpdate methods work

Imagine having a tool that can automatically detect if you are using JPA and Hibernate properly. Hypersistence Optimizer is that tool!

Introduction

In this article, I’m going to show you how the JPA persist and merge work and how do they compare with the Hibernate save, update, and saveOrUpdate methods.

Although you should favor the JPA-based entity state transition methods, you are going to see that the Hibernate-specific update is actually a good alternative to merge when you want to reduce the number of SQL queries being executed during a batch processing task.

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How to log the database transaction id using MDC (Mapped Diagnostic Context)

Imagine having a tool that can automatically detect if you are using JPA and Hibernate properly. Hypersistence Optimizer is that tool!

Introduction

In this article, I’m going to show you how you can log the database transaction id associated with a given SQL statement using the MDC (Mapped Diagnostic Context) feature offered by many logging frameworks.

If you are writing data access code, you have to use logging. As I explained in this article, using a JDBC proxy tool like datasource-proxy or p6spy is the best approach to logging SQL statements.

With datasource-proxy, you can easily build a JUnit extension to automatically detect N+1 query issues. For more details, check out the db-util open-source project.

Since JPA and Hibernate generate SQL statements on your behalf based on the entity state transitions executed by the data access layer, using logging is mandatory as you need to acknowledge that the auto-generated SQL statements are both effective and efficient.

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The best way to call a stored procedure with JPA and Hibernate

Imagine having a tool that can automatically detect if you are using JPA and Hibernate properly. Hypersistence Optimizer is that tool!

Introduction

In this article, you are going to learn the best way to call a stored procedure when using JPA and Hibernate so that the underlying JDBC resources are released as soon as possible.

I decided to write this article since the way Hibernate handles stored procedures can lead to ORA-01000: maximum open cursors exceeded issues on Oracle as explained in this Hibernate forum thread or StackOverflow question.

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