Sometimes it is useful to first define an abstraction. A good abstraction can reveal that some problems could be solved by the same solution. A good abstraction also makes it easier for us to communicate about the solution and understand its properties.
One such abstraction which I think should be defined and named is nonenumerable database. A database where you can query a value by a key, but you cannot enumerate all keys (nor all values). Even a database operator/administrator is not be able to do so.
At the same time, some problems are more intuitive than others and can help us better understand or even inform the abstraction. We will look at three examples where nonenumerable database can help: DNS/DNSSEC, gun ownership registry, and voting.
Database-abstraction APIs where you write a query using the host programming language should not exist. Or more precisely, should not have to exist. For example, in Django you can query the database using the following Python code:
Which Django translates (roughly) into the following SQL:
SELECT * FROM blog_entry WHERE is_draft = true;
But why we cannot write SQL query directly as an SQL query, while retaining all other features Django offers through its database-abstraction API (database agnostic code, inputs to queries and outputs from queries being Python objects, etc.)? I claim there is no reason anymore for that.