Gerald Britton <gerald.britton@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:
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.
