Andrey Lepikhov <a.lepik...@postgrespro.ru> writes: > Can we include the CustomScan node in the list of nodes that do not > support projection?
That seems like a pretty bad idea. Maybe it's a good thing for whatever unspecified extension you have in mind right now, but it's likely to be a net negative for many more. As an example, if some custom extension has a better way to calculate some output expression than the core code does, a restriction like this would prevent that from being implemented. > Reason is that custom node can contain quite arbitrary logic that does > not guarantee projection support. I don't buy this for a minute. Where do you think projection is going to happen? There isn't any existing node type that *couldn't* support projection if we insisted that that be done across-the-board. I think it's mostly just a legacy thing that some don't. regards, tom lane