Where database blog posts get flame-broiled to perfection
Ah, yes. "Learn ClickHouse CTE examples." How... quaint. One must assume the target audience for this literary gem consists of individuals who believe the WITH clause was invented last Tuesday by a plucky startup in Palo Alto. The sheer novelty of it all! It's as if they've unearthed some lost Dead Sea Scroll of declarative programming, rather than a feature that has been part of the SQL standard for, oh, a couple of decades now. But I digress. The medium is, as they say, the message, and a blog post is a fittingly ephemeral vessel for such fleeting knowledge.
Let's not dance around the real issue here. We are discussing ClickHouse. A "database" in the same sense that a child's lemonade stand is a multinational beverage corporation. It's a columnar store, an OLAP engine, a magnificent device for answering the question "how many terabytes of user-activity logs did we generate this morning?" with breathtaking speed. And for what? At what cost?
Frankly, it's the cost of the very soul of data management. I imagine the design meeting went something like this:
"Alright team, we need blazing-fast analytics. What parts of foundational computer science can we jettison? Codd's 12 rules? Throw 'em out, who's Codd? The 'C' in ACID? Consistency is for cowards! The entire concept of normalization? Just denormalize it until the heat-death of the universe! It'll be fine!"
They speak of "simplifying complex queries" as if they are bestowing a great gift upon the unwashed masses of so-called "data engineers." What they mean is providing a syntactic pacifier for those who would be utterly lost if asked to compose a non-trivial query using basic relational algebra. These Common Table Expressions are not a sign of sophistication; they are a crutch. They are the intellectual equivalent of putting guardrails on a bowling lane.
One shudders to think what their "performance tips" entail. I'm sure it's a laundry list of sins against the formal model:
It's a masterclass in wilful ignorance. They've stumbled backward into the CAP theorem, looked at Consistency, Availability, and Partition Tolerance, and decided that consistency was the one to ceremonially execute in the town square for the crime of being "too slow." They've built an entire architecture on a foundation of "eventual consistency," which is industry jargon for "the right answer will show up... eventually. Maybe. Don't worry about it."
Clearly they've never read Stonebraker's seminal work on the "one size fits all" fallacy. They are using a specialized analytical engine and celebrating its ability to perform a standard SQL feature, all while blissfully unaware of the vast theoretical landscape they are trampling through with muddy boots. It's tragic, really. All of this knowledge, decades of rigorous, peer-reviewed research, is available in journals and papers, yet they'd rather read a blog post with a catchy title written by someone whose chief qualification is knowing how to configure a Docker container.
But please, do go on. Tell me more about your "real-world use cases." I'm certain they are revolutionary.
Thank you for sharing this. I shall now go and wash my eyes with a first-edition copy of C.J. Date's An Introduction to Database Systems. Rest assured, this will be the last time I consult such a... practical resource. Cheerio.