sszabo@bigpanda.com writes:
>> Well, but why PgSQL ignore function result if any argument is NULL. IMHO is
>> function's problem what return, and PgSQL must use this result.
>
> I believe this is a known issue that's being looked at right now.
Current plans are to fix it in the release-after-next (7.1).
As you say, the behavior is correct for standard SQL operators; the
only real problem is that user-written operators might want to return
non-null results for null inputs, and we can't handle that right now.
Applying COALESCE before calling the operator will get the job done
in some cases, but it clutters your queries...
regards, tom lane