[SQL] polymorphic function in 7.4 vs. 8.3

[Richard Rosenberg]

I have the following setup which works great in version 8.3 but throws an 
error in 7.4:


CREATE TABLE atest1
(
  id integer NOT NULL,
  descr text,
  CONSTRAINT atest1_pkey PRIMARY KEY (id)
);



CREATE OR REPLACE FUNCTION test_trg()
  RETURNS "trigger" AS
'
DECLARE
any_rec wfsys.atest1;

BEGIN
any_rec.id := NEW.id;
any_rec.descr := NEW.descr;
select into any_rec * from dd_test(any_rec);
--any_rec := dd_test(any_rec);
RETURN any_rec;
END;
'
  LANGUAGE 'plpgsql' VOLATILE;


CREATE OR REPLACE FUNCTION dd_test(anyelement)
  RETURNS record AS
'
DECLARE
any_rec alias for $1;
some_row record;
BEGIN
some_row := any_rec;
if some_row.id < 0 then
raise notice ''id is < 0!'';
some_row.descr := ''some other value'';
end if;
RETURN some_row;
END;
'
  LANGUAGE 'plpgsql' VOLATILE;

CREATE TRIGGER trg_atest1
  BEFORE INSERT
  ON atest1
  FOR EACH ROW
  EXECUTE PROCEDURE test_trg();

Finally, firing the trigger like so:

insert into wfsys.atest1 values(123, 'some text');

Gives the following error:

ERROR:  column "any_rec" does not exist
CONTEXT:  PL/pgSQL function "test_trg" line 7 at select into variables


** Error **

ERROR: column "any_rec" does not exist
SQL state: 42703
Context: PL/pgSQL function "test_trg" line 7 at select into variables


It works great on 8.3 (my dev server),  but throws the error on the machine I 
am forced to work with, which is running version 7.4. I realize that 
polymorphic functions were pretty new in v7.4, is there a workaround or am I 
making a silly mistake? Or both? 

Incidentally, I get the same error when I change the polymorphic function's 
argument from "anyelement" to "wfsys.atest1" so it seems that it is occurring 
in the trigger function.  Thanks for any help.

Richard

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Re: [SQL] polymorphic function in 7.4 vs. 8.3

[Richard Rosenberg]

Tom, thanks for your prompt reply. I think I may have my head on straight now, 
this should work:

CREATE TABLE atest1
(
  id integer NOT NULL,
  descr text,
  CONSTRAINT atest1_pkey PRIMARY KEY (id)
);


CREATE OR REPLACE FUNCTION test1_trg()
  RETURNS trigger AS
'
DECLARE
    some_rec public.atest1;

BEGIN
some_rec.id := NEW.id;
some_rec.descr := NEW.descr;
select into some_rec * from dd_test(some_rec) as (id int4, descr text);
--some_rec := dd_test(some_rec);
RETURN some_rec;
END;
'
  LANGUAGE 'plpgsql' VOLATILE;


CREATE OR REPLACE FUNCTION dd_test(anyelement)
  RETURNS record AS
'
DECLARE
    any_row alias for $1;
    some_row record;

BEGIN
    some_row := any_row;
    if some_row.id < 0 then
        raise notice ''id is < 0!'';
        some_row.descr := ''some other value'';
    end if;
    
RETURN some_row;
END;
'
  LANGUAGE 'plpgsql' VOLATILE;


CREATE TRIGGER trg_atest1
  BEFORE INSERT
  ON atest1
  FOR EACH ROW
  EXECUTE PROCEDURE test1_trg();

insert into public.atest1 values(123, 'some text');

insert into public.atest1 values(-90, 'some text');

This gives the same result. Also in the trigger function test1_trg the syntax 
of the call to the polymorphic function makes a difference in terms of the 
error that is thrown. A simple assignment like:

. . .
some_rec := dd_test(some_rec);
. . .

Throws a syntax error, while a 'SELECT INTO. . .' like:

. . .
select into some_rec * from dd_test(some_rec) as (id int4, descr text);
. . .

Throws this:

 ERROR: column "some_rec" does not exist
SQL state: 42703
Context: PL/pgSQL function "test1_trg" line 7 at select into variables

Sorry for the earlier typo(s), and thanks for any help. 

Richard

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Re: [SQL] polymorphic function in 7.4 vs. 8.3

[Richard Rosenberg]

On Thursday 11 June 2009 14:49:46 Tom Lane wrote:

> Sure you can't move the DB off 7.4?  There would be pretty considerable
> benefits from adopting some recent release instead.
>
>   regards, tom lane

Don't I know it. I am SOL as the machine is hosted/shared out by an external 
provider. I can do it by getting rid of the polymorphism - breaking the 
columns into separate args - as you say:

CREATE OR REPLACE FUNCTION public.test1_trg()
  RETURNS "trigger" AS
'
DECLARE
some_rec public.atest1;

BEGIN
some_rec.id := NEW.id;
some_rec.descr := NEW.descr;
select into some_rec * from dd_test(some_rec.id, some_rec.descr, TG_RELNAME) 
as (id int, descr text);
--some_rec := dd_test(some_rec)::public.atest1;
RETURN some_rec;
END;
'
  LANGUAGE 'plpgsql' VOLATILE;


CREATE OR REPLACE FUNCTION public.dd_test(int, text, text)
  RETURNS record AS
'
DECLARE
any_id alias for $1;
any_descr alias for $2;
tablename alias for $3;
some_id integer;
some_descr text;
some_row record;

BEGIN
some_id := any_id;
if some_id < 0 then
raise notice ''id is < 0!'';
some_descr := ''some other value'';
end if;
for some_row in execute ''select * from ''||tablename||'' where 1 = 0'' loop
end loop;
some_row.id := some_id;
some_row.descr := some_descr;
RETURN some_row;
END;
'
  LANGUAGE 'plpgsql' VOLATILE;

Oh well, I'm glad I tested the approach out before going too far down this  
road. Thanks again for your timely help. 

Richard

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