On Oct 11, 2018, at 10:35 AM, David Fetter <da...@fetter.org> wrote: > >> It didn't get far, but you may want to take a look at a rejected patch for >> copy_srf() (set returning function) >> https://www.postgresql.org/message-id/CADkLM%3DdoeiWQX4AGtDNG4PsWfSXz3ai7kY%3DPZm3sUhsUeev9Bg%40mail.gmail.com >> https://commitfest.postgresql.org/12/869/ >> >> Having a set returning function gives you the full expressiveness of SQL, >> at the cost of an extra materialization step. > > I wonder whether something JIT-like could elide this. A very > interesting subset of such WHEN clauses could be pretty > straight-forward to implement in a pretty efficient way.
Are you thinking something like having a COPY command that provides results in such a way that they could be referenced in a FROM clause (perhaps a COPY that defines a cursor…)?
