It is commonly stated and I found it to be very true. PostgreSQL is quite advanced in its procedural aspects (Oracle isn't too far behind either) but they were not made with particular focus on debugging. I'll need to have hacks like creating temp tables to dump records at a given stage vs simply setting a breakpoint. I can unit test the shit out of bog standard Java code; PL/SQL for all its capabilities doesn't even come close. The one area this tilts to the other side is when you need to do heavy processing with high volume of data on database side; a well written stored proc would handily outperform application side logic simply due to the network latency involved. But for typical use cases, putting complex business logic in stored procs just isn't worth it.

The context here was that it’s not free, as I understood it. So, moving logic to the database, might make it faster, but that doesn’t mean that it’s instantaneous or that I no longer have to think about the scaling concerns of it.

So, personally, I read that section as “logic in the database is not a zero cost abstraction.