How to fix Array subscript error in PostgreSQL

-- WRONG: Accessing index 0
SELECT my_array[0];

-- CORRECT: Access index 1 for the first element
SELECT my_array[1];

-- Check the length of the first dimension
SELECT array_length(my_array, 1) AS array_size;

-- Safe access with bounds checking
SELECT 
  CASE 
    WHEN idx BETWEEN 1 AND array_length(my_array, 1) 
    THEN my_array[idx]
    ELSE NULL 
  END AS safe_value
FROM table_name;

SELECT 
  array_lower(my_array, 1) AS lower_bound,
  array_upper(my_array, 1) AS upper_bound;

-- Safe loop in PL/pgSQL
FOR i IN array_lower(my_array, 1) .. array_upper(my_array, 1) LOOP
  RAISE NOTICE 'Element: %', my_array[i];
END LOOP;

-- Create a 3x2 array filled with NULL
DECLARE
  my_array INT[][];
BEGIN
  my_array := array_fill(NULL::INT, ARRAY[3, 2]);
  -- Now safe to assign to any position within [1:3][1:2]
  my_array[2][1] := 42;
END;

CREATE FUNCTION safe_array_access(arr INT[], idx INT) RETURNS INT AS $$
BEGIN
  IF idx < array_lower(arr, 1) OR idx > array_upper(arr, 1) THEN
    RETURN NULL;
  END IF;
  RETURN arr[idx];
END;
$$ LANGUAGE plpgsql IMMUTABLE;