Yay for Clang

Posted Jan 27, 2026 13:09 UTC (Tue) by Wol (subscriber, #4433)
In reply to: Yay for Clang by farnz
Parent article: GNU C Library 2.43 released

> and your refusal to accept the mathematical proof that MV is a strict subset of relational in terms of what a database can do, since there is a 1:1 (in terms of number of operations) translation of MV into relational, but not the other way round.

So how come modern relational databases are only now catching up with MV as far as what the actual database itself is capable of?

> Note that this doesn't mean that any implementation of relational is inherently better - after all, an MV design could well have better developer experience than a relational design - but that a technically perfect relational database can do everything any MV database can, with the same performance as, or better than, an MV database.

And again, why does a SQL query need an optimiser? MV doesn't have an optimiser, because it's an easy proof it costs more than it saves.

Anyway, we're getting off topic and one of the editors will probably be stomping on this pretty quickly.

Cheers,
Wol

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Yay for Clang

Posted Jan 27, 2026 13:24 UTC (Tue) by farnz (subscriber, #17727) [Link]

For the first point - just because something is technically better in theory does not mean that all implementations are inherently better. Compare MySQL and PostgreSQL, for example - they both implement the same theory, yet do not have the same feature sets.

For the second: because SQL is not a great representation of relational, and you need an optimizer to go from the SQL query to a decent relational query. In addition, relational allows you to simply describe some very complex queries that in MV are simply not possible, and the optimizer allows the database engine to find a fast way to perform that query - where in MV, you just don't do that because you can't.

Put another way, those questions are like "why are planes not as good as buses at taking me on a 50 mile trip? Why do planes need autopilots, when buses don't - it's easy to show that an autopilot for buses would cost more than it saves?".