Re: Row pattern recognition

Vik Fearing <vik@postgresfriends.org>

From: Vik Fearing <vik@postgresfriends.org>

To: Tatsuo Ishii <ishii@postgresql.org>, david.g.johnston@gmail.com

Cc: jacob.champion@enterprisedb.com, pgsql-hackers@postgresql.org, er@xs4all.nl, peter@eisentraut.org

Date: 2024-10-22T13:12:43Z

Lists: pgsql-hackers

Commits

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

Add temporal FOREIGN KEY contraints
- 89f908a6d0ac 18.0 cited
Remove obsolete executor cleanup code
- d060e921ea5a 17.0 cited

On 22/10/2024 12:19, Tatsuo Ishii wrote:
> Acording to ISO/IEC 9075-2:2016 "4.21.2 Row pattern navigation operations",
>
>    <row pattern navigation operation> evaluates a <value expression> VE
>    in a row NR, which may be different than current row CR.
>
>  From this I think PREV(col + 1) should be interpreted as:
>
> 1. go to the previous row.
> 2. evaluate "col + 1" at the current row (that was previous row).
> 3. return the result.
>
> If my understanding is correct, prev(price + 1) has the same meaning
> as prev(price) + 1.



This is how I read the specification also.

-- 

Vik Fearing