Обсуждение: plpgsql NULL statement (was Re: [GENERAL] Postgres 8.0 -> BEGIN EXCEPTION END Syntax????)

Daniel Schuchardt <daniel_schuchardt@web.de> writes:
> BEGIN
>   exception ...
> EXCEPTION
>   WHEN OTHERS THEN ?????????????what to write for do nothing?????????
> END;

> in oracle it's
> WHEN OTHERS THEN null;
> but this syntax doesn't work in postgres.

In Postgres you just write nothing at all:
BEGIN...EXCEPTION  WHEN OTHERS THENEND;

However, it does appear that Oracle's PL/SQL has such a statement,
and that they don't like empty exception sections (or empty if/then/else
arms, etc), but *require* you to write "NULL;" in these places.
It seems to me that it would ease porting of Oracle functions if
we allowed a NULL statement in plpgsql.

It looks like about five minutes' work to add such a thing ... anyone
have any objections?
        regards, tom lane

Tom Lane said:
> Daniel Schuchardt <daniel_schuchardt@web.de> writes:
>> BEGIN
>>   exception ...
>> EXCEPTION
>>   WHEN OTHERS THEN ?????????????what to write for do nothing?????????
>> END;
>
>> in oracle it's
>> WHEN OTHERS THEN null;
>> but this syntax doesn't work in postgres.
>
> In Postgres you just write nothing at all:
>
>     BEGIN
>     ...
>     EXCEPTION
>       WHEN OTHERS THEN
>     END;
>
> However, it does appear that Oracle's PL/SQL has such a statement, and
> that they don't like empty exception sections (or empty if/then/else
> arms, etc), but *require* you to write "NULL;" in these places.
> It seems to me that it would ease porting of Oracle functions if
> we allowed a NULL statement in plpgsql.
>
> It looks like about five minutes' work to add such a thing ... anyone
> have any objections?
>

It's got my vote :-) PLSQL is based on Ada and this is an Ada rule. I like
the PLSQL/Ada way a lot more than the PostgreSQL example you gave above,
which just looks ... odd.

cheers

andrew

On Mon, 16 Aug 2004, Tom Lane wrote:

> > in oracle it's
> > WHEN OTHERS THEN null;
> > but this syntax doesn't work in postgres.
> 
> It looks like about five minutes' work to add such a thing ... anyone
> have any objections?

Is NULL above an empty statement in oracle or is it a normal expression
(the normal NULL value) so that the above is a shorthand for
  WHEN OTHERS THEN SELECT NULL;

?

-- 
/Dennis Björklund

Dennis Bjorklund <db@zigo.dhs.org> writes:
> Is NULL above an empty statement in oracle or is it a normal expression

It's an actual empty statement.

> (the normal NULL value) so that the above is a shorthand for
>    WHEN OTHERS THEN SELECT NULL;

Even if it were, the point here is to accept standard Oracle coding
without any translation of that sort.
        regards, tom lane