Re: access numeric data in module

On Mon, Sep 9, 2024 at 2:02 PM Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> By that argument, we should move every declaration in every .c file
> into c.h and be done. I'd personally be happier if we had *not*
> exposed the other data structure details you mention, but that
> ship has sailed.

Not every declaration in every .c file is of general interest, but the
ones that are probably should be moved into .h files. The on-disk
representation of a commonly-used data type certainly qualifies.

You can see from Chapman's reply that I'm not making this up: when we
don't expose things, it doesn't keep people from depending on them, it
just makes them copy our code into their own repository. That's not a
win. It makes those extensions more fragile, not less, and it makes
the PostgreSQL extension ecosystem worse. pg_hint_plan is another,
recently-discussed example of this phenomenon: refuse to give people
the keys, and they start hot-wiring stuff.

> If we do do what you're advocating, I'd at least insist that the
> declarations go into a new file numeric_internal.h, so that it's
> clear to all concerned that they're playing with fire if they
> depend on that stuff.

I think that's a bit pointless considering that we don't do it in any
of the other cases. I'd rather be consistent with our usual practice.
But if it ends up in a separate header file that's still better than
the status quo.

--
Robert Haas
EDB: http://www.enterprisedb.com