Horton

Row pattern recognition

David G. Johnston <david.g.johnston@gmail.com>

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From: "David G. Johnston" <david.g.johnston@gmail.com>
To: Tatsuo Ishii <ishii@postgresql.org>
Cc: "jacob.champion@enterprisedb.com" <jacob.champion@enterprisedb.com>, "vik@postgresfriends.org" <vik@postgresfriends.org>, "pgsql-hackers@postgresql.org" <pgsql-hackers@postgresql.org>, "er@xs4all.nl" <er@xs4all.nl>, "peter@eisentraut.org" <peter@eisentraut.org>
Date: 2024-10-22T05:29:34Z
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 Monday, October 21, 2024, Tatsuo Ishii <ishii@postgresql.org> wrote:
>
> I wonder how "PREV(col + 1)" is different from "PREV(col) + 1".
> Currently my RPR implementation does not allow PREV(col + 1). If
> "PREV(col + 1)" is different from "PREV(col) + 1", it maybe worthwhile
> to implement "PREV(col + 1)".
>

Interesting feature that I’m now just seeing.

The expression PREV(column_name) produces a value output taken from the
given named column in the preceding frame row.  It doesn’t make any sense
to me to attempt to add the integer 1 to an identifier that is being used
as a value input to a “function”.  It would also seem quite odd if “+ 1”
had something to do with row selection as opposed to simply being an
operator “+(column_name%type, integer)” expression.

Maybe RPR is defining something special here I haven't yet picked up on, in
which case just ignore this.  But if I read: “UP as price > prev(price +
1)” in the opening example it would be quite non-intuitive to reason out
the meaning.  “Price > prev(price) + 1” would mean my current row is at
least one (e.g. dollar per share) more than the value of the previous
period.

David J.