I am surprised by this example, for the same reason.
Generally, performance is a top cause of abstraction leaks and the emergence of less-than-beautiful code. On an infinitely powerful machine it would be easy and advisable to program using neat abstracrions, using purely "the language of" the business. Our machines are not infinitely powerful, and that is especially evident when larger data sets are involved. That's where, to achieve useful performance, you have to increasingly speak "the language of" the machine. This is inevitable, and the big part of the programmer's skill is to be able to speak both "languages", to know when to speak which one, and produce readable code regardless.
Database programming is a prime example. There's a reason, for example, why ORMs are very messy and constitute such excellent footguns: they try to gap this bridge, but inevitably fail in important ways. And having and ORM in the example would, most likely, violate the "functional core" principle from the article.
So it looks like the author accidentally presented a very good counterexample to their own idea. I like the idea though, and I would love to know how to resolve the issue.
Generally, performance is a top cause of abstraction leaks and the emergence of less-than-beautiful code. On an infinitely powerful machine it would be easy and advisable to program using neat abstracrions, using purely "the language of" the business. Our machines are not infinitely powerful, and that is especially evident when larger data sets are involved. That's where, to achieve useful performance, you have to increasingly speak "the language of" the machine. This is inevitable, and the big part of the programmer's skill is to be able to speak both "languages", to know when to speak which one, and produce readable code regardless.
Database programming is a prime example. There's a reason, for example, why ORMs are very messy and constitute such excellent footguns: they try to gap this bridge, but inevitably fail in important ways. And having and ORM in the example would, most likely, violate the "functional core" principle from the article.
So it looks like the author accidentally presented a very good counterexample to their own idea. I like the idea though, and I would love to know how to resolve the issue.