Tag Archives: database

Schema migration, an important part of continuous delivery

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Most of you have a relational database involved in your persistence. As soon as your first version has been set in use, you can’t change the database schema as easy anymore or you might lose valuable production data.

At the same time, continuous delivery demands that there should be as few manual steps as possible. See here for motivation on continuous delivery.

You no longer have a few database instance, there are numerous for different levels of testing and every developer nowadays run a personal database. To keep track of all database instances and keep them updated becomes a steep task.

To tackle this, we started using Flyway as a tool to manage our database scripts. Our applications migrates the database automatically on startup so we get a hands-free solution that will guarantee that the code and database schema is in sync.

Here is a technical recipe for accomplishing this when using Flyway in combination with Spring.
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Why I am excited about Datomic

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Background
A couple of years ago, I watched this talk/video called “Are we there yet” by Rich Hickey. In it he sorts out a way of thinking about identity, value, state and time. That view feels quite natural and is maybe even close to reality as we perceive it. He moves on to persistent data structures and different techniques to get from one state to the next. How to progress from one immutable value to the next (e.g. STM). And multiversion concurrency control. Watch the video.

Following that reasoning, Clojure is a natural consequence. Interesting because of the ideas above, built in.

Moreover, when this thinking makes it into a database like Datomic, that’s even more interesting.

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