Jeff Davis <pgsql@j-davis.com> writes:
> Are you saying we make special cases for all of the "obvious" functions,
> and they should behave differently from user-defined functions?
It's possible to special-case any particular function you really feel
you need this behavior for. We did special-case || (the string
concatenation operator), and there was some discussion of also putting
in a built-in special case for LIKE, but we desisted from sliding any
further down that slippery slope. Since it's possible for users to
install such hacks for themselves, as in the example here,
http://archives.postgresql.org/pgsql-general/2007-11/msg00538.php
there didn't seem to be a convincing case for weakening the type
checking for everybody.
regards, tom lane