Re: Row pattern recognition

From: Tatsuo Ishii <ishii(at)postgresql(dot)org>
To: assam258(at)gmail(dot)com
Cc: david(dot)g(dot)johnston(at)gmail(dot)com, vik(at)postgresfriends(dot)org, jacob(dot)champion(at)enterprisedb(dot)com, er(at)xs4all(dot)nl, peter(at)eisentraut(dot)org, pgsql-hackers(at)postgresql(dot)org
Subject: Re: Row pattern recognition
Date: 2026-01-04 12:28:25
Message-ID: 20260104.212825.376854799362558025.ishii@postgresql.org
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Hi Henson,

>> Here do you have "ONE ROW PER MATCH" option of RPR in your mind? In my
>> understanding it's in MATCH_RECOGNIZE clause, but not in RPR in Window
>> clause. (ALL ROWS PER MATCH is not applicable either in RPR in
>> Window clause).
>>
>>
> You're absolutely right - thank you for the correction!
>
> I'm currently exploring what this NFA structure could theoretically
> support, rather than strictly binding to the spec yet. Since I'm
> still learning from Oracle manuals and your code without access to
> the full SQL:2016 standard, I mixed up MATCH_RECOGNIZE syntax with
> Window clause RPR - sorry for the confusion!

No problem at all. MATCH_RECOGNIZE and Window clause RPR are quite
similar. In the mean time "Trino" manual maybe useful for you if you
don't have access to the SQL standard.
https://trino.io/docs/current/sql/pattern-recognition-in-window.html

Best regards,
--
Tatsuo Ishii
SRA OSS K.K.
English: http://www.sraoss.co.jp/index_en/
Japanese:http://www.sraoss.co.jp

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