Re: HASH partitioning not working properly

On Fri, Jun 19, 2020 at 11:44 AM David Rowley <dgrowleyml(at)gmail(dot)com> wrote:

> On Fri, 19 Jun 2020 at 17:42, Srinivasa T N <seenutn(at)gmail(dot)com> wrote:
> > After seeing the below, I feel partitioning is not working properly
> or it maybe case that my understanding is wrong. Can somebody explain me
> what is happening?
>
> > postgres=# select * from busbar_version6;
> > objectid | ver_id
> > ----------+--------
> > (0 rows)
> >
> > postgres=# select * from busbar_version7;
> > objectid | ver_id
> > ----------+--------
> > 6 | 6
> > (1 row)
> >
> > Why second insert has gone to table busbar_version7 instead of
> busbar_version6?
>
> It's your understanding that's not correct. The value of is passed
> through a hash function and the partition is selected based partition
> matching the remainder value after dividing the return value of the
> hash function by the largest modulus of any partition.
>
> That might surprise you, but how would you select which partition a
> varchar value should go into if you didn't use a hash function.
>
> David
>

How can I see the output of hash function that is used internally?

Regards,
Seenu.