I am currently researching the best practises (at a reasonably high level) for application design for highly maintainable systems which result in minimal friction to change. By “Data Tier” I mean database design, Object Relation Mappers (ORMs) and general data access technologies.
From your experiences, what have you found to be the common mistakes & bad practises when it comes to data tier development and what measures have you taken / put in place / or can recommend to make the data tier a better place to be from a developer perspective?
An example answer may include: What is the most common causes of a slow, poorly scalable and extendible data tiers? + What measures can be taken (be it in design or refactoring) to cure this issue?
I am looking for war stories here and some real world advice that I can build into publicly available guidance documents and samples.
Magic.
I have used Hibernate, which automatically stores and fetches objects from a database. It also supports lazy loading, so that a related object is only retrieved from the database when you ask for it. This works in some magic way I don’t understand.
This all works fine as long as it works, but when it breaks down it is impossible to track it down. I think we had a problem when we combined Hibernate with AOP, that somehow the object was not yet initialized by Hibernate when our code was executed. This problem was very hard to debug, because Hibernate works in such mysterious ways.