Обсуждение: regexp_replace( , , , NULL ) returns null?

Is there any particular reason for this:

decibel@decina.local=# SELECT regexp_replace( 'a', 'a', 'b', null ) IS NULL;?column?
----------t
(1 row)

ISTM it’d be a lot better if it treated NULL flags the same as ‘’...
--
Jim Nasby, Lead Data Architect   (512) 569-9461

Jim Nasby <jnasby@enova.com> writes:
> Is there any particular reason for this:
> decibel@decina.local=# SELECT regexp_replace( 'a', 'a', 'b', null ) IS NULL;
>  ?column? 
> ----------
>  t
> (1 row)

Yeah: regexp_replace is strict.

> ISTM it�d be a lot better if it treated NULL flags the same as ��...

In Oracle's universe that probably makes sense, but to me it's not
sensible.  Why should "unknown" flags produce a non-unknown result?

I find it hard to envision many use-cases where you wouldn't actually
have the flags as a constant, anyway; they're too fundamental to the
behavior of the function.
        regards, tom lane

On 5/2/14, 8:57 PM, Tom Lane wrote:
> Jim Nasby <jnasby@enova.com> writes:
>> ISTM it’d be a lot better if it treated NULL flags the same as ‘’...
>
> In Oracle's universe that probably makes sense, but to me it's not
> sensible.  Why should "unknown" flags produce a non-unknown result?

Only because they're more options than data.

> I find it hard to envision many use-cases where you wouldn't actually
> have the flags as a constant, anyway; they're too fundamental to the
> behavior of the function.

Unless you're wrapping this function; handling the case of the flags being optional becomes easier then.

(FWIW, I'm creating a version that accepts an array of search/replace arguments.)
-- 
Jim Nasby, Lead Data Architect   (512) 569-9461