Berkeley DB is an ideal database system for applications that need fast, scalable, and reliable embedded database management. For applications that need different services, however, it can be a poor choice.
First, do you need the ability to access your data in ways you cannot predict in advance? If your users want to be able to enter SQL queries to perform complicated searches that you cannot program into your application to begin with, then you should consider a relational engine instead. Berkeley DB requires a programmer to write code in order to run a new kind of query.
On the other hand, if you can predict your data access patterns up front -- and in particular if you need fairly simple key/value lookups -- then Berkeley DB is a good choice. The queries can be coded up once, and will then run very quickly because there is no SQL to parse and execute.
Second, are there political arguments for or against a standalone relational server? If you're building an application for your own use and have a relational system installed with administrative support already, it may be simpler to use that than to build and learn Berkeley DB. On the other hand, if you'll be shipping many copies of your application to customers, and don't want your customers to have to buy, install, and manage a separate database system, then Berkeley DB may be a better choice.
Third, are there any technical advantages to an embedded database? If you're building an application that will run unattended for long periods of time, or for end users who are not sophisticated administrators, then a separate server process may be too big a burden. It will require separate installation and management, and if it creates new ways for the application to fail, or new complexities to master in the field, then Berkeley DB may be a better choice.
The fundamental question is, how closely do your requirements match the Berkeley DB design? Berkeley DB was conceived and built to provide fast, reliable, transaction-protected record storage. The library itself was never intended to provide interactive query support, graphical reporting tools, or similar services that some other database systems provide. We have tried always to err on the side of minimalism and simplicity. By keeping the library small and simple, we create fewer opportunities for bugs to creep in, and we guarantee that the database system stays fast, because there is very little code to execute. If your application needs that set of features, then Berkeley DB is almost certainly the best choice for you.
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