Re: Dynamic binding in plpgsql function

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

regards

Pavel Stehule

>        RETURN x;
>    END;
>    $$ LANGUAGE 'plpgsql';
>
> I don't want to do an EXECUTE statement since I have no table to put after the FROM clause. I want to assign the resulting value directly to a variable like in my example.
>
> Can I/How can I achieve this?
>
> Thanks,
>
> Pierre
>
>
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