The article talks about how CTEs are efficiency minefields and how Postgres doesn't do a good job of pushing down predicates, for example.

TBH, the solution is to improve the Postgres engine in this regard?

For example, in Bigquery I often use CTEs and see predictable speedups that are explained by predicate pushdown when slapping a WHERE clause on the user of a CTE etc. Bigquery has plenty of performance gotchas but I don't think CTEs are one of them; they seem to be transparent to the optimiser.

Something else that Bigquery supports is user-defined 'table' functions. These are like the 'functors' the article creates.

However, in practice they aren't very widely used, and I think this hints that they aren't as useful as the article is hoping for.

The thing I _really_ want is scoping. If only functions could be described like CTE WITH blocks, e.g.

   WITH visits AS (
      SELECT ...
      FROM web_logs
      WHERE ...
   ),
   foo(bar INT, baz STRING) AS (
      ... function body here
   )
   SELECT ..., foo(a, b), ...
   FROM visits
   WHERE ...

Apart from the tidiness of this, this allows inlining of functions into the SQL statement body rather than as separate statements. Often various tooling e.g. DBT makes it really hard to with separate function definitions etc, and being able to inline logic would make things possible.

Bigquery also supports user-defined aggregate functions. Although there is rarely the need to stray from the standard builtin aggregate functions, when you need them they are brilliant.

(Anyone working _on_ Bigquery reading? If so, please ping me, I have loads of feedback on what works well and where the user pain and toil is ;) )