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From: Jonathan S. Katz <jkatz@postgresql.org>
To: Erwin Brandstetter <brsaweda@gmail.com>
To: pgsql-docs <pgsql-docs@postgresql.org>
Subject: Re: ROWS vs RANGE in release notes for pg 16
Date: Fri, 18 Aug 2023 21:03:12 -0400
Message-ID: <9272ffff-3cdb-ebe4-4f4a-a89ea2081be0@postgresql.org> (raw)
In-Reply-To: <CAGHENJ5VteqniBgrih7=gzpzLcELTpUfUNNB2PGg+Ae6o1As=g@mail.gmail.com>
References: <CAGHENJ5VteqniBgrih7=gzpzLcELTpUfUNNB2PGg+Ae6o1As=g@mail.gmail.com>

Hi Erwin,

On 8/18/23 7:41 PM, Erwin Brandstetter wrote:
> The release notes for Postgres 16 says here:
> https://www.postgresql.org/docs/16/release-16.html#RELEASE-16-PERFORMANCE <https://www.postgresql.org/docs/16/release-16.html#RELEASE-16-PERFORMANCE;
> 
>  > Allow window functions to use ROWS mode internally when RANGE mode is 
> specified but unnecessary (David Rowley)
> 
> But the fix also applies to the much more common case where no mode has 
> been specified, RANGE unfortunately being the default - including the 
> most common use case "row_number() OVER (ORDER BY col)". This is what 
> made me investigate, test and eventually propose a fix in the first 
> place. See:
> 
> https://www.postgresql.org/message-id/flat/CAGHENJ7LBBszxS%2BSkWWFVnBmOT2oVsBhDMB1DFrgerCeYa_DyA%40m... <https://www.postgresql.org/message-id/flat/CAGHENJ7LBBszxS%2BSkWWFVnBmOT2oVsBhDMB1DFrgerCeYa_DyA%40m...;
> https://www.postgresql.org/message-id/flat/CAApHDvohAKEtTXxq7Pc-ic2dKT8oZfbRKeEJP64M0B6%2BS88z%2BA%4... <https://www.postgresql.org/message-id/flat/CAApHDvohAKEtTXxq7Pc-ic2dKT8oZfbRKeEJP64M0B6%2BS88z%2BA%4...;
> 
> Also, I was hoping to get a mention in the release note for working this 
> out:
> 
>  > Allow window functions to use the faster ROWS mode internally when 
> RANGE mode is specified or would be used by default, but unnecessary 
> (David Rowley, Erwin Brandstetter)

Thanks for flagging. I suggest adding the comment to the release notes 
thread on -hackers:

https://www.postgresql.org/message-id/flat/ZGaPa7M3gc2THeDJ%40momjian.us

Jonathan



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  Subject: Re: ROWS vs RANGE in release notes for pg 16
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