Обсуждение: PL/pgSQL proposal: using list of scalars in assign stmts, fore and fors stmts

Hello

Now, statements EXECUTE INTO and SELECT INTO allow using list of scalars. 
FORe and FORs allow only ROW o RECORD VARIABLE. I'll plan and I did it 
enhance this stmts:

<for> := FOR <target> IN {SELECT | EXECUTE} ... LOOP
<target> := {row|record|comma separated list of scalar vars}

<assign> := <target2> ':=' <expression>
<target2> := {row|record|variable|'ROW(' comma separated list of scalar vars 
')'}

for example:
CREATE OR REPLACE FUNCTION test(OUT _rc, OUT _x varchar, OUT _y varchar)
RETURNS SETOF RECORD  AS $$
DECLARE _r RECORD;
BEGIN rc := 0; -- old style; FOR _r IN SELECT generate_series AS x, generateseries + 1 AS y FROM 
generate_series(1,4) LOOP   _rc := _rc + 1; _x := _r.x; _y := _r.y;   RETURN NEXT; END LOOP; -- new one FOR _x,_y IN
SELECTgenerate_series, generateseries + 1 FROM 
 
generate_series(1,4) LOOP   _rc := _rc + 1;   RETURN NEXT; END LOOP; -- new two   FOR _r IN SELECT generate_series AS
x,generateseries + 1 AS y FROM 
 
generate_series(1,4)    LOOP   _rc := _rc + 1; ROW(_x,_y) := _r;   RETURN NEXT; END LOOP; RETURN;
END; $$ LANGUAGE plpgsql;

any comments?
Regards
Pavel Stehule

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"Pavel Stehule" <pavel.stehule@hotmail.com> writes:
> <for> := FOR <target> IN {SELECT | EXECUTE} ... LOOP
> <target> := {row|record|comma separated list of scalar vars}

This part seems all right to me.

> <assign> := <target2> ':=' <expression>
> <target2> := {row|record|variable|'ROW(' comma separated list of scalar vars 
> ')'}

As I already said on -patches, I consider this a bad idea.  It's too
error prone (because there's no easy way of seeing what the field order
will be).  And it doesn't add anything that you can't do now.  I think
a series of "var = rec.field" assignments is a preferable way to do it.
        regards, tom lane

On Thu, Dec 22, 2005 at 10:18:16AM +0100, Pavel Stehule wrote:
> Hello
> 
> Now, statements EXECUTE INTO and SELECT INTO allow using list of scalars. 
> FORe and FORs allow only ROW o RECORD VARIABLE. I'll plan and I did it 
> enhance this stmts:
> 
> <for> := FOR <target> IN {SELECT | EXECUTE} ... LOOP
> <target> := {row|record|comma separated list of scalar vars}
> 
> <assign> := <target2> ':=' <expression>
> <target2> := {row|record|variable|'ROW(' comma separated list of scalar 
> vars ')'}

How about:

<target2> := {row|record|variable|'[ROW](' comma separated list of scalar vars ')'}

instead, where the ROW is optional?

Cheers,
D
-- 
David Fetter david@fetter.org http://fetter.org/
phone: +1 415 235 3778

Remember to vote!

David Fetter <david@fetter.org> writes:
> How about:
> <target2> := {row|record|variable|'[ROW](' comma separated list of scalar vars ')'}
> instead, where the ROW is optional?

If we're going to do this at all (which I'm still agin), I think the ROW
keyword is important to minimize ambiguity.  If you are allowed to start
a statement with just "(x, ..." then there will be way too many
situations where the parser gets confused by slightly bad input,
resulting in way-off-base syntax error reports.  Or worse, no syntax
error, but a function that does something else than you expected.

I know that ROW is optional in the bit of SQL syntax that this proposal
is based on, but that's only because the SQL spec says we have to, not
because it's a good idea.
        regards, tom lane

Tom Lane wrote:

>David Fetter <david@fetter.org> writes:
>  
>
>>How about:
>><target2> := {row|record|variable|'[ROW](' comma separated list of scalar vars ')'}
>>instead, where the ROW is optional?
>>    
>>
>
>If we're going to do this at all (which I'm still agin), I think the ROW
>keyword is important to minimize ambiguity.  If you are allowed to start
>a statement with just "(x, ..." then there will be way too many
>situations where the parser gets confused by slightly bad input,
>resulting in way-off-base syntax error reports.  Or worse, no syntax
>error, but a function that does something else than you expected.
>
>I know that ROW is optional in the bit of SQL syntax that this proposal
>is based on, but that's only because the SQL spec says we have to, not
>because it's a good idea.
>
>
>  
>

I see no virtue in this either. It strikes me as just more syntactic 
sugar, and unless I am misreading or out of date it would be another 
incompatibility with Oracle. I don't mind doing that, but I think it 
should be for a better reason than that it accords with someone's taste 
in syntactic style. I'd be somewhat more persuaded if Oracle did this. I 
also agree with Tom's comments about requiring ROW. As I observed 
regarding another syntax proposal, terseness is not always good, and 
redundancy is not always bad.

cheers

andrew