Postgres Pro
Downloads
Home   >   mailing lists

Thread: Length returns NULL ?

Length returns NULL ?

From
Marcos Pegoraro
Date:
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

Re: Length returns NULL ?

From
Erik Wienhold
Date:
On 2024-06-05 19:50 +0200, Marcos Pegoraro wrote:
> There are some functions called ...length, but only array_length returns
> NULL on empty array, why ?

Because the empty array has zero dimensions[1].  But now I'm wondering
why array_ndims returns NULL instead of zero for empty arrays.

[1] https://www.postgresql.org/message-id/603c8f070811061951u16034c3fk5dfaa493a6739a24%40mail.gmail.com

-- 
Erik