Using a common database for collaborative development

Question

Some of the people in my project seem to think that using a common development database with everyone connecting to it is the best thing. I think that it isn't and each developer having his own database (with periodic updated data dumps) is the best. Am I right or wrong? Have you encountered any problems in any of these approaches?

Answer 1

Disk space and CPU should be cheap enough that every developer can run their own instance of the database, with an automated build under version control. This is needed to allow developers to be bold in hacking on the database, in isolation from any other developer's concurrent hacking.

The caveat being, of course, that any changes they make to their private instance are useless to anyone else unless it can be automatically applied during the build process. So there needs to be a firm policy that application code can't depend on any database state unless that state is represented by version-controlled, unit-tested changes to the DDL.

For an excellent guide on the theory and practice of treating the database definition as another part of the project code, and coordinating changes and refactorings, see Refactoring Databases: Evolutionary Database Design by Scott W. Ambler and Pramod Sadalage.

Answer 2

I like having my own copy of the database for development, because it gives you the flexibility to rapidly change things without worrying how it will impact others.

However, if all the developers are hacking away on their own copy of the database, it becomes more and more difficult to merge everyone's work together in the end.

I think you can get the best of both worlds by letting developers work on a local copy during day-to-day development, but each developer should probably merge their work into a common copy on a pretty regular basis. Writing a lot of unit tests helps too.

Answer 3

We share a single database amongst all our developer (20-odd) but we've got it structured so that everyone has their own tables.

You don't need a separate database per developer if you structure the application right. It should be configurable which database or table-prefix it uses anyway so you can easily move it between instances (unit test, system test, acceptance test, production, disaster recovery and so on).

The advantage to using a single database is that the cost of maintenance is amortized. You don't have your DBAs trying to handle a lot of databases (or, if you're a small-DB shop, you don't have every developer trying to maintain their own database when they're better utilized in developing).

Answer 4

Having a single point of Failure is not a good thing isn't it?

Answer 5

I prefer a single, shared database. But it's very dependent on the situation and the applications being developed.

What works for me may not work for you. Go with your gut.

Answer 6

If you are working with Hibernate or any hibernate-based platform you can configure your database to be created when you start your server (create-drop option). This is very useful when you are adding new attributes to your classes. If this is the case each developer must have his own copy of the DB.

If you are not changing the DB structure at all then you can use a single shared DB. In this second case is not a must. I prefer to have my own DB where I can do whatever I want. On the other hand remember that some queries can take a lot of time and this will affect your whole team if you are sharing a DB.