Re: [HACKERS] Re: PL/PGSQL function with parameters

Tom Lane wrote:
> Michael Ansley <Michael(dot)Ansley(at)intec-telecom-systems(dot)com> writes:
> > CREATE FUNCTION table_count(varchar) RETURNS integer AS '
> > DECLARE
> > SQL varchar;
> > RES integer;
> > BEGIN
> > SQL = ''SELECT * INTO temp1 FROM '' || $1;
> > EXECUTE SQL;
> > SELECT count(*) INTO RES FROM temp1;
> > RETURN(RES)
> > END;
> > '
> > LANGUAGE 'plpgsql';
>
> > What I couldn't get it to do was to select directly into the variable RES.
>
> I tried this, and it seems that "SELECT ... INTO foo" is not executed
> correctly by EXECUTE --- the INTO is handled as an ordinary select-into-
> table construct rather than plpgsql's select-into-variable.
>
> While I have not looked closely, I seem to recall that plpgsql handles
> INTO by stripping that clause out of the statement before it's passed to
> the SQL engine. Evidently that's not happening in the EXECUTE case.
>
> Jan, do you agree this is a bug? Is it reasonable to try to repair it
> for 7.1? If we do not change the behavior of EXECUTE now, I fear it
> will be too late --- some people will come to depend on the existing
> behavior.

EXECUTE simply takes the string expression and throws it into
SPI_exec() without parsing. Changing that for 7.1 is *not*
possible.

The above can be accomplished by

DECLARE
ROW record;
RES integer;
BEGIN
FOR ROW IN EXECUTE
''SELECT count(*) AS N FROM '' || $1
LOOP
RES := N;
END LOOP;
RETURN RES;
END;

Not as elegant as it should be, but at least possible.
There's much to be done for a future version of PL/pgSQL, but
better support for dynamic SQL needs alot of functionality
added to the main parser and the SPI manager in the first
place.

Jan

--

#======================================================================#
# It's easier to get forgiveness for being wrong than for being right. #
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