Re: automatically generating node support functions

I wrote:
> Andres Freund <andres(at)anarazel(dot)de> writes:
>> Additionally, I think we've had to add tags to the enum in minor releases
>> before and I'm afraid this now would end up looking even more awkward?

> Peter and I already had a discussion about that upthread --- we figured
> that if there's a way to manually assign a nodetag's number, you could use
> that option when you have to add a tag in a stable branch. We didn't
> actually build out that idea, but I can go do that, if we can solve the
> more fundamental problem of keeping the autogenerated numbers stable.

> One issue with that idea, of course, is that you have to remember to do
> it like that when back-patching a node addition. Ideally there'd be
> something that'd carp if the last autogenerated tag moves in a stable
> branch, but I'm not very sure where to put that.

One way to do it is to provide logic in gen_node_support.pl to check
that, and activate that logic only in back branches. If we make that
part of the branch-making procedure, we'd not forget to do it.

Proposed patch attached.

regards, tom lane