Re: htup header reorganization breaks many extension modules

Excerpts from Peter Eisentraut's message of mié sep 26 11:18:51 -0300 2012:
> On 9/26/12 10:07 AM, Tom Lane wrote:
> > I can't get excited about this either. This isn't the first, or the
> > last, change that add-on modules can expect to have to make to track
> > newer Postgres versions. If we allow Peter's complaint to become the
> > new project policy, we'll never be able to make any header
> > rearrangements at all, nor change any internal APIs.
>
> I'm not saying we can never change anything about the internal headers,
> but we can make a small effort not to create useless annoyances.

I proposed a possible way out of the problem elsewhere. Please comment
on that.

> That said, could someone clarify the header comments in the new headers?
> We currently have
>
> * htup.h
> * POSTGRES heap tuple definitions.
>
> * htup_details.h
> * POSTGRES heap tuple header definitions.

htup.h is what you need if you want to pass tuples around. It's
particularly useful for other headers that want to declare their
functions as receiving or returning tuples. htup_details.h is what you
need if you want to operate on tuples, such as creating them or
examining them.

I guess those comments aren't all that well thought out; suggestions
welcome.

> The names of the headers don't match their documented purpose very much.
> Is GETSTRUCT a "detail" of the heap tuple definition, or is it related
> to "tuple headers"? It's not really either, but I guess it is related
> to tuple headers because you need to know about the headers to get to
> the stuff past it.

> When I see headers stuff.h and stuff_details.h, it makes me think that
> you should only use stuff.h, and stuff_details.h are internal things.
> But a lot of external modules use GETSTRUCT, so they might get confused.

The other proposal was htup_internal.h but that would have been much
more indicative of stuff that's supposed to be used only for internal
consumption of files in backend/access/heap and such, which is why I
stayed away from that name. I think htup_details.h is a good enough
compromise.

--
Álvaro Herrera http://www.2ndQuadrant.com/
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