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How should existing data exist if the structure of an object has been modified or deleted by GAE?

GAE recommends using JDO / JPA. But I have a serious question about using OODB as they are. JDO based on user class structure. And the data structure must constantly change as the service progresses. Thus,

  • If a property of the data (entity) class is deleted, what happened to existing data about this property?
  • If a data (entity) class is renamed for refactoring, how does JDO know this renaming? Or all data loss?

The main point: "How does JDO / GAE / BigTable apply a modification of the application level structure (class / attributes) to existing data in the database?".

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See Updating Model Schema .

  • Existing objects will still have the old property. New objects will not be.
  • You can map a new entity class to an existing type in the data warehouse. However, if you want to change the Kind name in the data warehouse, then this is not so simple.
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Source: https://habr.com/ru/post/1310519/

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