Re: HASH partitioning not working properly - Mailing list pgsql-general

From David Rowley
Subject Re: HASH partitioning not working properly
Date
Msg-id CAApHDvra1kLN=GXc=fA0OHLz3ub2ThXwhe8P7a-Qo3-T73wV0w@mail.gmail.com
Whole thread Raw
In response to HASH partitioning not working properly  (Srinivasa T N <seenutn@gmail.com>)
Responses Re: HASH partitioning not working properly
List pgsql-general
On Fri, 19 Jun 2020 at 17:42, Srinivasa T N <seenutn@gmail.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



pgsql-general by date:

Previous
From: Kyotaro Horiguchi
Date:
Subject: Re: Conflict with recovery on PG version 11.6
Next
From: Srinivasa T N
Date:
Subject: Re: HASH partitioning not working properly