Re: Add PGDLLEXPORT to PG_FUNCTION_INFO_V1

On 18 October 2016 at 04:19, Andres Freund <andres@anarazel.de> wrote:
> On 2016-10-17 16:16:37 -0400, Robert Haas wrote:
>> I wouldn't think that cross-file references would be especially
>> common.  Functions that take PG_FUNCTION_ARGS and return Datum aren't
>> a lot of fun to call from C.  But maybe I'm wrong.
>
> There's a fair number of DirectFunctionCall$Ns over the backend.

It's only an issue if one contrib calls another contrib (or the core
backend code calls into a contrib, but that's unlikely) via
DirectFunctionCall .

If changed to use regular OidFunctionCall they'll go via the catalogs
and be fine, albeit at a small performance penalty. In many cases that
can be eliminated by caching the fmgr info and using FunctionCall
directly, but it requires taking a lock on the function or registering
for invalidations so it's often not worth it.

Personally I think it'd be cleaner to avoid one contrib referencing
another's headers directly and we have the fmgr infrastructure to make
it unnecessary. But I don't really think it's a problem that
especially needs solving either.

-- Craig Ringer                   http://www.2ndQuadrant.com/PostgreSQL Development, 24x7 Support, Training & Services