Google AppEngine : Lazy Data Migration with Versions
If you have already used Google AppEngine to develop an application, you would have already scratched your head around data migration. And Google App Engine is not that great when it comes to Agile style iterations of web development. In its own way, it forces you to design models up front instead of making life easier evolving over time. I have been developing a community application, 'Yes to Politics' for friends in Andhra Pradesh, India to interact with politics in some strangely different way. More about this app later, let me share about data migration. I have around 28000 entities in a model and trust me, I tried to cover all my needs in the design of the model up front. Well, software development doesn't work that way. I realized I needed another property in the model and I needed to give some default value too. When you add a new property to an existing model, Google App engine doesn't fill the default value for the existing set of entities. So when you acc...