![]() Primary keys uniquely identify rows in a table. There are two types of keys in SQL: primary and foreign. These databases receive the “relational” qualifier because “related” tables are connected together by keys. ![]() In its simplest form, the relational data model is a collection of tables containing rows of data. Relational databases have been around for almost 50 years. In this article, I’ll discuss why primary keys are important, different types of keys you can use, and a primary key with values that are guaranteed to have never, ever been used in the entire universe (with a 1/10^37 chance of error). ![]() Because of its importance, we have to give special consideration to how we select our primary keys. The foundation for a table in a relational database is the primary key. Relational databases are highly intertwined, so one small change can have unexpected, cascading effects. For more details about this topic, check out this article.Changing the schema for large relational databases costs companies millions of dollars every year. However, while auto-generating a UUID identifier when using Hibernate is fairly easy, the standard UUIDs are not a good fit for Primary Keys, as you are better off using a time-sorted TSID instead. The latter option requires providing an implementation of the .UUIDGenerationStrategy which is rather straightforward. You can either allow Hibernate to use the Java-based UUID generation strategy, or you can delegate this task to the database. If you enjoyed this article, I bet you are going to love my Book and Video Courses as well. I'm running an online workshop on the 20-21 and 23-24 of November about High-Performance Java Persistence. Notice the calls to the uuid_generate_v4 PostgreSQL function which is used to assign the UUID identifier values. "insert into post (title, id) values (?, ?)" Now, when persisting 3 Post entities, Hibernate generates the following SQL statements: The attribute is used to customize the UUID generation strategy via the uuid_gen_strategy_class parameter value which takes the fully-qualified class name of the .UUIDGenerationStrategy interface implementation. The uuid2 strategy stands for .UUIDGenerator which we want to use instead of the legacy .UUIDHexGenerator that’s registered under the uuid name in Hibernate. To provide the PostgreSQLUUIDGenerationStrategy to our Post entity, we have to use the Hibernate-specific = "post") Now, we can call the uuid_generate_v4 function to get a variant 4 UUID based on IETF RFC 4122 specification. In our case, 4 stands for variant 4 (random) generator strategy.īecause we are using PostgreSQL, we also need to create the uuid-ossp extension before using the UUID-specific functions:ĬREATE EXTENSION IF NOT EXISTS "uuid-ossp" The getGeneratedVersion method defines what type of UUID we are generating, according to the IETF RFC 4122 standard. Throw new IllegalArgumentException("Can't fetch a new UUID") ResultSet resultSet = statement.executeQuery( Statement statement = connection.createStatement() Hibernate generates the following SQL INSERT statement: ![]() tTitle("High-Performance Java Persistence") Getters and setters omitted for brevity However, few might know that GenerationType.AUTO can be used for UUID identifiers as = "post") When using JPA, we can use the GenerationType.AUTO strategy of the annotation to assign numerical identifier automatically, based on an IDENTITY column, a SEQUENCE or the infamous TABLE generator. Now, let’s see how we can map the Post entity so that the UUID identifier be auto-generated for us. The Post entity has a UUID identifier and a title. In this article, we are going to see how to use a UUID entity identifier that is auto-generated by Hibernate either in the JVM or using database-specific UUID functions. So, enjoy spending your time on the things you love rather than fixing performance issues in your production system on a Saturday night! Well, Hypersistence Optimizer is that tool!Īnd it works with Spring Boot, Spring Framework, Jakarta EE, Java EE, Quarkus, or Play Framework. Follow having a tool that can automatically detect JPA and Hibernate performance issues.
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