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: 2026-01-07 03:21:54
Message-ID: 20260107.122154.1592214576851480438.ishii@postgresql.org
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Hi Henson,

Thank you for the design proposal. I'm still learning it, and I have a
few questions for now.

> 3. Proper Lexical Order support
> - Respects PATTERN alternative order for ONE ROW PER MATCH

RPR in WINDOW clause does not allow to specify "ONE ROW PER MATCH".
(nor ALL ROWS PER MATCH). So I am not sure what you mean here.

> 4. GREEDY/RELUCTANT quantifier support
> - Longest vs shortest match semantics
>
> 5. Incremental MEASURES computation
> - Aggregate values computed during matching, no rescan needed

In my understanding MEASURES does not directly connect to Aggregate
computation with rescan. Can you elaborate why implementing MEASURES
allows to avoid recan for aggregate computation?

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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