Peter Geoghegan <peter@2ndquadrant.com> writes:
> Clearly deprecating rules implies some loss of functionality - there
> is no exact, drop-in equivalent to something that magically rewrites
> SQL that isn't equally baroque and problematic. If that's the bar,
> then detractors of rules should stop wasting their breath, because the
> bar has been set impossibly high.
I believe an advice system is a good contender here, as already
proposed here:
http://archives.postgresql.org/pgsql-hackers/2012-10/msg00610.php
See defadvice in Emacs Lisp and The Standard Method Combination of the
Common Lisp Object System as sources of inspiration here.
http://www.gnu.org/software/emacs/manual/html_node/elisp/Advising-Functions.html
http://www.gigamonkeys.com/book/object-reorientation-generic-functions.html
It basically would be rules without the multiple evaluation risks, yet
still the multiple evaluation feature when you need it, and with
explicit control over it.
Then if you insist on comparing to a macro facility, as we're talking
about dynamic code rewriting, maybe we need to compare RULEs to the lisp
style macro facility, which is nothing like a pre-processor facility (in
lisp, that's the reader, I think).
Regards,
--
Dimitri Fontaine
http://2ndQuadrant.fr PostgreSQL : Expertise, Formation et Support