Re: Dynamic binding in plpgsql function

2011/3/2 Merlin Moncure <mmoncure(at)gmail(dot)com>

> On Tue, Mar 1, 2011 at 5:17 PM, Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com>
> wrote:
> > Hello
> >
> > 2011/3/2 Pierre Racine <Pierre(dot)Racine(at)sbf(dot)ulaval(dot)ca>:
> >> Hi,
> >>
> >> I would like to write a generic plpgsql function with a text parameter
> being a callback function name so that my general function can call this
> callback function. e.g.:
> >>
> >> CREATE OR REPLACE FUNCTION ST_MyCallbackFunction(y int)
> >> RETURNS int AS $$
> >> DECLARE
> >> BEGIN
> >> RETURN someCalculationBasedOnY;
> >> END;
> >> $$ LANGUAGE 'plpgsql';
> >>
> >> CREATE OR REPLACE FUNCTION ST_MyGeneralFunction(callback text)
> >> RETURNS SETOF geomval AS $$
> >> DECLARE
> >> x integer;
> >> y integer;
> >> BEGIN
> >> y := somecalculation;
> >> x := 'callback'(y); --This is what I need
> >
> > EXECUTE 'SELECT ' || callback || '($1)' USING y INTO x;
> >
> > there are no other way than EXECUTE
> >
> > attention - there is a sql injection risk
>
> another way if you are willing to write some C is to wrap and expose
> OidFunctionCall1 so it takes oid of function you want to call.
>
As always, Merlin shows the uncommon thinking! :-)
Respect!

>
> merlin
>
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--
// Dmitriy.