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From: Marcos Pegoraro <[email protected]>
To: Postgres General <[email protected]>
Subject: Length returns NULL ?
Date: Wed, 5 Jun 2024 14:50:26 -0300
Message-ID: <CAB-JLwZmKYDT=0WSkvKHLqaejxWoMjBok3YjUtAtM1U8=N__0g@mail.gmail.com> (raw)

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

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