Moshe Jacobson <moshe@xxxxxxxxxxxx> writes: > The function pulls a GUC value and that's all it does. Is it safe to mark > it IMMUTABLE? No; such a function is by definition mutable. > I noticed that if I updated the GUC variable and ran the > query again, it worked as I would hope, with the new value of the function > substituted. So it seems it would be safe, but I'd like to verify. You might chance to get away with that as long as you never ever use the function in a view or prepared query (including inside a plpgsql function). But it seems likely to bite you eventually. > I'd also like to know why it wouldn't work if the function was STABLE: > Since Postgres should know that it's not going to change over the course of > the query, couldn't it substitute the value as well? You have not shown us the context, but I suspect you are wishing that the planner would assume that the function's result can't change between planning and execution. Unfortunately, it can. regards, tom lane -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
