Introduction Testing against the same database you use in production is crucial for catching environment-specific bugs early. However, setting up Oracle locally has traditionally been painful—complex licensing, heavy resource requirements, and tedious configuration.
Enter Oracle Free (formerly Oracle XE) with Docker. Oracle now provides lightweight, free Docker images that make local Oracle development surprisingly easy. Combined with Spring Boot’s Docker Compose support, you can spin up a real Oracle database automatically when your application starts.
Over the last few weeks, I’ve been tinkering with some parts of our persistence layer — mostly out of curiosity. I’ve been using Spring Data JPA forever, but recently I started pushing it into areas where the “happy path” begins to crumble: dynamic filtering, projections, and of course… the infamous N+1 problem.
During this little experiment, I ended up rediscovering QueryDSL (yes, it still exists, still works, and is still pretty awesome).
I also stumbled upon something fun: using LISTAGG (Oracle/H2) to flatten collections in a single query, avoiding N+1 without fetch-joining the universe.