It's like functions that return functions: SQL that generates SQL. Normally, in PG land, one generates code using SQL, using the format() function, then one EX

It's like functions that return functions: SQL that generates SQL. Normally, in PG land, one generates code using SQL, using the format() function, then one EXECUTEs it. That would still be the case for generated FUNCTION bodies, naturally, but for everything else you could just use DDLs on a small and well-tested metaschema that does this work for you. Just as in Lisp you might rather not use eval but instead use macros, here you'd prefer to use DDLs on a metaschema over DMLs. Hygiene is one of the motivators. And yes, you could DELETE from a view that represents columns instead of using ALTER TABLE ... DROP COLUMN ... All the usual transactional semantics apply. You can BEGIN, delete that row, and rollback, leaving the DB unchanged.