Re: [HACKERS] Macros bundling RELKIND_* conditions

On 2017-Aug-02, Tom Lane wrote:

> I think Peter's got the error and the detail backwards.  It should be
> more like
>
> ERROR: "someview" cannot have constraints
> DETAIL: "someview" is a view.
>
> If we do it like that, we need one ERROR message per error reason,
> and one DETAIL per relkind, which should be manageable.

I support this idea.  Here's a proof-of-concept patch that corresponds
to one of the cases that Ashutosh was on about (specifically, the one
that uses the RELKIND_CAN_HAVE_STORAGE macro I just added).  If there
are no objections to this approach, I'm going to complete it along these
lines.

I put the new function at the bottom of heapam.c but I think it probably
needs a better place.

BTW are there other opinions on the RELKIND_HAS_STORAGE vs.
RELKIND_CAN_HAVE_STORAGE debate?  I'm inclined to change it to the
former.