Horton

Re: Row pattern recognition

Vik Fearing <vik@postgresfriends.org>

View thread
From: Vik Fearing <vik@postgresfriends.org>
To: Chao Li <li.evan.chao@gmail.com>, Tatsuo Ishii <ishii@postgresql.org>
Cc: david.g.johnston@gmail.com, jacob.champion@enterprisedb.com, er@xs4all.nl, peter@eisentraut.org, pgsql-hackers@postgresql.org
Date: 2025-11-18T11:19:46Z
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 →

  1. Add temporal FOREIGN KEY contraints

  2. Remove obsolete executor cleanup code

On 18/11/2025 06:03, Chao Li wrote:
> 1 - 0001 - kwlist.h
> ```
> +PG_KEYWORD("define", DEFINE, RESERVED_KEYWORD, BARE_LABEL)
> ```
>
> Why do we add “define” as a reserved keyword? From the SQL example you put in 0006:
> ```
> <programlisting>
> SELECT company, tdate, price,
>   first_value(price) OVER w,
>   max(price) OVER w,
>   count(price) OVER w
> FROM stock
>   WINDOW w AS (
>   PARTITION BY company
>   ORDER BY tdate
>   ROWS BETWEEN CURRENT ROW AND UNBOUNDED FOLLOWING
>   AFTER MATCH SKIP PAST LAST ROW
>   INITIAL
>   PATTERN (LOWPRICE UP+ DOWN+)
>   DEFINE
>    LOWPRICE AS price &lt;= 100,
>    UP AS price &gt; PREV(price),
>    DOWN AS price &lt; PREV(price)
> );
> </programlisting>
> ```
>
> PARTITION is at the same level as DEFINE, but it’s not defined as a reserved keyword:
> ```
> PG_KEYWORD("partition", PARTITION, UNRESERVED_KEYWORD, BARE_LABEL)
> ```
>
> Even in this patch,”initial”,”past”, “pattern” and “seek” are defined as unreserved, why?
>
> So I just want to clarify.


Because of position. Without making DEFINE a reserved keyword, how do 
you know that it isn't another variable in the PATTERN clause?

-- 

Vik Fearing