Ken Tanzer <ken.tanzer@xxxxxxxxx> writes: > On Sat, Jul 20, 2019 at 7:46 AM Tom Lane <tgl@xxxxxxxxxxxxx> wrote: >> and then to add insult to injury, has to search pg_description a second >> time for each hit. > Not sure if I'm understanding this correctly, but are you saying that > because col_description() is specified in two places in the query, that it > actually will get called twice? Yes. > I was under the impression that a function > (at least a non-volatile one) specified multiple times, but with the same > arguments, would only get called once. Is that just wishful thinking? Afraid so. There's been assorted talk about various optimizations to avoid unnecessary duplicate function calls, but I don't think that merging textually-separate calls has even been on the radar. The discussions I can recall have been more about not calling stable functions (with fixed arguments) more than once per query. regards, tom lane
