Improve aggregate function in PL/pgSQL - sql

Question

I've tried to create an aggregate function, which finds the minimum value in a column, then it adds the Laplacian noise.
I am using Postregres PL/pgSQL language.
The aggregate works perfectly, but I'd like to know if there is any way to improve the code that I wrote.
/*
* PLpgSQL function which behaves to aggregate the MIN(col) function then adds the laplacian noise.
* For the sensivity (which is the upper bound of the query), We use the halfed maximum value of the column called.
* Passing the array which contains the entire column values, that will be compared, to establish which one is the minimum.
* Then we compute Laplacian distribution (sensivity/epsilon). This given value is added to the minimum Value that will disturb
* the final result
*/
CREATE OR REPLACE FUNCTION addLaplacianNoiseMin (real[]) RETURNS real AS $$
DECLARE
i real;
minVal real; --minimum value which is found in the column and then disturbed
laplaceNoise real; --laplacian distribution which is computed finding the halfed maximum value, divided by an arbitrary epsilon (small value)
epsilon real := 1.2;
sensivity real; --our computed upper bound
maxVal real;
BEGIN
minVal := $1[1];
maxVal := $1[1];
IF ARRAY_LENGTH($1,1) > 0 THEN --Checking whether the array is empty or not
<<confrontoMinimo>>
FOREACH i IN ARRAY $1 LOOP --Looping through the entire array, passed as parameter
IF minVal >= i THEN
minVal := i;
ELSE
maxVal := i;
END IF;
END LOOP confrontoMinimo;
ELSE
RAISE NOTICE 'Invalid parameter % passed to the aggregate function',$1;
--Raising exception if the parameter passed as argument points to null.
RAISE EXCEPTION 'Cannot find MIN value. Parameter % is null', $1
USING HINT = 'You cannot pass a null array! Check the passed parameter';
END IF;
sensivity := maxVal/2;
laplaceNoise := sensivity/(epsilon);
RAISE NOTICE 'minVal: %, maxVal: %, sensivity: %, laplaceNoise: %', minVal, maxVal, sensivity,laplaceNoise;
minVal := laplaceNoise + minVal;
RETURN minVal;
END;
$$ LANGUAGE plpgsql;
CREATE AGGREGATE searchMinValueArray (real)
(
sfunc = array_append,
stype = real[],
finalfunc = addLaplacianNoiseMin,
initCond = '{}'
);

Answer 1

Yes, you can improve that by not using an array as state for the aggregate, but a composite type like:
CREATE TYPE aggstate AS (minval real, maxval real);
Then you can perform the operation from your loop in the SFUNC and don't have to keep an array in memory that can possibly become very large. The FINALFUNC would then become very simple.