Horton
Menu

Re: Row pattern recognition

Tatsuo Ishii <ishii@postgresql.org>

View thread
From: Tatsuo Ishii <ishii@postgresql.org>
To: assam258@gmail.com
Cc: vik@postgresfriends.org, er@xs4all.nl, jacob.champion@enterprisedb.com, david.g.johnston@gmail.com, peter@eisentraut.org, pgsql-hackers@postgresql.org
Date: 2026-02-17T09:00:53Z
Lists: pgsql-hackers 
Hi Henson,

>> What do you mean by "Anchored pattern" here? I am asking because R010
>> (RPR in Window clause) does not allow to use anchors (^ and $) in
>> PATTERN clause.
>>
> 
> Good catch - the term "anchored pattern" is indeed confusing here.
> You're absolutely right that SQL:2023 R010 does not allow regex anchors
> (^ and $) in the PATTERN clause.
> In this context, I was using "anchored" to mean "a pattern that starts
> with a PREFIX element" - not referring to regex anchors at all. The
> example "START A+ B" has a PREFIX element (START) that "anchors" the
> pattern matching to begin at a specific point.

Ok.

> To avoid confusion with SQL regex anchors, I suggest we change the
> terminology:
> 
> "Anchored pattern" → "Pattern with PREFIX" or "PREFIX-led pattern"

I like "Pattern with PREFIX".

> "Anchored pattern absorption" → "PREFIX pattern absorption optimization"

Looks good.

> The optimization issue remains the same: PREFIX elements block the
> absorption mechanism, requiring the "shadow path" approach to maintain
> O(n) complexity while processing patterns like "START A+ B".
> Does this clarification make sense?

Yes!

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

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. Adjust cross-version upgrade tests for seg_out() fix

  2. Rationalize error comments in partition split/merge tests

  3. Add fast path for foreign key constraint checks

  4. Fix assorted pretty-trivial memory leaks in the backend.

  5. Add temporal FOREIGN KEY contraints

  6. Add trailing commas to enum definitions

  7. Remove obsolete executor cleanup code