Hi Amul, I share others opinion that this feature is useful.
>> On Fri, 25 Aug 2023 at 03:06, Vik Fearing <vik@postgresfriends.org> wrote: >>> >>> >>> I don't like this part of the patch at all. Not only is the >>> documentation only half baked, but the entire concept of the two >>> commands is different. Especially since I believe the command should >>> also create a generated column from a non-generated one. >> >> >> But I have to agree with Vik Fearing, we can make this patch better, should we? >> I totally understand your intentions to keep the code flow simple and reuse existing code as much >> as possible. But in terms of semantics of these commands, they are quite different from each other. >> And in terms of reading of the code, this makes it even harder to understand what is going on here. >> So, in my view, consider split these commands. > > > Ok, probably, I would work in that direction. I did the same thing that > SET/DROP DEFAULT does, despite semantic differences, and also, if I am not > missing anything, the code complexity should be the same as that.
If we allow SET EXPRESSION to convert a non-generated column to a generated one, the current way of handling ONLY would yield mismatch between parent and child. That's not allowed as per the documentation [1]. In that sense not allowing SET to change the GENERATED status is better. I think that can be added as a V2 feature, if it overly complicates the patch Or at least till a point that becomes part of SQL standard.
Yes, that going to be a bit complicated including the case trying to convert the non-generated column of a child table where need to find all the ancestors