Re: BUG #18205: Performance regression with NOT NULL checks.

From: Andres Freund <andres(at)anarazel(dot)de>
To: Daniel Migowski <dmigowski(at)ikoffice(dot)de>
Cc: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, "pgsql-bugs(at)lists(dot)postgresql(dot)org" <pgsql-bugs(at)lists(dot)postgresql(dot)org>
Subject: Re: BUG #18205: Performance regression with NOT NULL checks.
Date: 2023-11-19 22:39:11
Message-ID: 20231119223911.rt73qzjykzxi6jcf@awork3.anarazel.de
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Hi,

On 2023-11-19 14:17:44 -0800, Andres Freund wrote:
> On 2023-11-19 21:15:37 +0000, Daniel Migowski wrote:
> > And yes, in my real world use case which I tried to understand I have a wide
> > table with 81 columns, and I am using column 1,43,18,75 and filter by
> > attribute 82,42, and 24.
>
> Are most of the columns NULL or not?

Another question: In the real query, how selective is the WHERE clause? In
your test query all rows are returned and you have no columns in the select
list, but it doesn't sound like that's quite your real workload...

Greetings,

Andres Freund

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