Love to see "return next" work like python yield! Anyone working on that?
On Sun, Jan 5, 2020, 5:46 PM Tom Lane <t...@sss.pgh.pa.us> wrote: > Gerald Britton <gerald.brit...@gmail.com> writes: > > Back to where I started in my top post: I became interested in this due > to > > the doc note on returning a cursor and that it can be an efficient way to > > handle large result sets. I suppose that implies lazy evaluation. Does > > that mean that if I need plpgsql for a function for he language's power > yet > > want the results to be returned lazily, a cursor is the (only?) way to > go? > > Nope. The docs' reference to a cursor only suggests that if you can > express the function's result as a single SQL query, then opening a > cursor for that query and returning the cursor name will work. But > if you need plpgsql to express the computation, that's not a terribly > helpful suggestion. > > If you'd like to see some actual movement on the missing feature about > lazy evaluation in FROM, you could help test/review the pending patch > about it: > > https://commitfest.postgresql.org/26/2372/ > > However, that still is only half of the problem, because you also need > a PL that is prepared to cooperate, which I don't believe plpgsql is. > I think (might be wrong) that a plpython function using "yield" can > be made to compute its results lazily. > > regards, tom lane >
