[PostgreSQL-Hackers] Version defines

This has been proposed and rejected before, mainly on the grounds that
it would encourage bad programming practices.

At compile time, you should be checking the specific feature you care
about, not a system version number (this is pretty much the entire point
behind Autoconf). At run time, you need to be making a run-time test
anyway; compiling against version x.y headers does not guarantee
anything about what version you will be executing against at runtime.

regards, tom lane

I admit that I am probably practicing this bad programming at few places
in my source, and shame on me for it. I have hoped to tighten it up a
bit later, but it is convenient for the time being.

Well, for one of my uses, it is not a feature check. My PL loads a
Python extension module whose path is dependent on the major and minor
version of the PostgreSQL installation that the PL was compiled against.
So I construct the module path string based on the major and minor at
compile time.


If this is the stance that the group has, that is fine. For now, I will
continue my shameful practice of parsing up pg_config --version and
defining the components for use in my source. (;

Er ... can't you just keep it in pkglibdir and refer to it via $libdir?
Given that 8.0 now supports relocatable installations, I'd think it best
to avoid hardwiring any paths at compile time.

regards, tom lane

Hmm..

I think it would be best to keep Python [extension] modules in Python's
site-packages.

AFA hardwiring is concerned, I will probably make it a GUC variable in
8.0 that will default to how I currently hardwire it.

FWIW, here's what I've been using in PL/R for a while now:

/* working with postgres 7.3 compatible sources */
#if (CATALOG_VERSION_NO <= 200211021)
#define PG_VERSION_73_COMPAT
#elif (CATALOG_VERSION_NO <= 200310211)
#define PG_VERSION_74_COMPAT
#else
#define PG_VERSION_75_COMPAT
#endif


Joe