plpgsql : looping over multidimensional array : getting NULL for subdimension

Use array_upper(aList, 2);
see the example, maybe can help u

CREATE OR REPLACE FUNCTION
xxx(
aList varchar[][])
returns TEXT as '
declare
myUpper1 integer;
myUpper2 integer;

myRet varchar := '''';
begin
myUpper1 := array_upper(aList, 1);
IF myUpper1 IS NULL THEN
myUpper1 := 0;
END IF;
myUpper2 := array_upper(aList, 2);
IF myUpper2 IS NULL THEN
myUpper2 := 0;
END IF;

FOR i in 1 .. myUpper1 LOOP
FOR k in 1 .. myUpper2 LOOP
myRet := myRet || aList[i][k];
END LOOP;
myRet := myRet || ''_'';
END LOOP;

RETURN myRet;
end;
'
LANGUAGE 'plpgsql';