Length returns NULL ?

[Marcos Pegoraro <marcos@xxxxxxxxxx>]

There are some functions called ...length, but only array_length returns NULL on empty array, why ?

select array_length('{}'::text[],1), -->NULL
       jsonb_array_length('[]'), -->0
       bit_length(''), -->0
       octet_length(''), -->0
       length(''), -->0
       char_length(''), -->0
       length(B''); -->0

I know, it is documented, but the question is, why does it work differently ?




array_length ( anyarray, integer ) → integer

Returns the length of the requested array dimension. (Produces NULL instead of 0 for empty or missing array dimensions.)




array_length(array[1,2,3], 1) → 3

array_length(array[]::int[], 1) → NULL

array_length(array['text'], 2) → NULL