[calmbonsai]

Correct. I think the parent commenter is confusing a language's concrete syntax with its abstract syntax. At the end of the day, the ease (or lack there of) of translating an AST into performant executing code is highly correlated with the potential variance of those ASTs.

The more higher-level expressions your languages supports, the more work its compiler (whether targeting physical or virtual hardware) must do to translate those ASTs into "machine" code and the higher the variance of that code during its execution workload.

It's even more work when that language's expressions are declarative instead of imperative.

[benzayb]

When a DBMS that claims it is relational and yet it supports SQL's "features" that departs from the relational model, then that DBMS is not relational.

If a DBMS is "slow" or "fast", that is not because of SQL -- it is because of the specific implementation decisions that the makers of that DBMS took.

And that has nothing to do with what you just said.