Re: Query optimiser is not using 'not null' constraint when 'order by nulls last' clause is used

From: Nandakumar M <m(dot)nanda92(at)gmail(dot)com>
To: "David G(dot) Johnston" <david(dot)g(dot)johnston(at)gmail(dot)com>
Cc: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Laurenz Albe <laurenz(dot)albe(at)cybertec(dot)at>, PostgreSQL mailing lists <pgsql-performance(at)postgresql(dot)org>
Subject: Re: Query optimiser is not using 'not null' constraint when 'order by nulls last' clause is used
Date: 2018-02-02 17:01:27
Message-ID: CANcFUu7o+xcppnDyjf64+BgmjjzT6me_G5spqAOwipU6hUNdvg@mail.gmail.com
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Hi,

On Fri, Feb 2, 2018 at 9:28 PM, David G. Johnston
<david(dot)g(dot)johnston(at)gmail(dot)com> wrote:

> You probably can (I assume the nulls aspect of the index doesn't prevent PK
> usage), but you must add the PK to the table after creating the index and
> not let the system auto-generate the index for you.
>
> https://www.postgresql.org/docs/10/static/sql-altertable.html
>
> ALTER TABLE name ADD PRIMARY KEY USING INDEX index_name;
>

I missed to notice this in the docs. Thank you David for pointing it out.

Regards,
Nanda

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