Re: Odd behavior with 'currval'

On Thu, Feb 8, 2018 at 10:58 AM, Steven Hirsch <snhirsch(at)gmail(dot)com> wrote:

> On a hunch, I tried 'SELECT currval(NULL)' to see if it returned '0', but
> that too returns NULL. So, where is the '0' coming from when I do:
>
> SELECT currval( pg_get_serial_sequence('udm_as
> set_type_definition','def_id'))
>
> ? I've already established that the inner expression evaluates to NULL!

​This is indeed unusual...to be specific here pg_get_serial_sequence
returns null in lieu of an error for being unable to locate the indicated
sequence. currval is returning null because it is defined "STRICT" and so
given a null input it will always return null. currval itself, when
provided a non-null input, is going to error or provide a number (which
should never be zero...).

I'm wondering whether someone didn't like the fact that currval errors and
instead wrote a overriding function that instead returns zero?

David J.