Date: Mon, 06 Oct 2025 09:09:01 +0900 (JST)
Message-Id: <20251006.090901.2288040209954599522.ishii@postgresql.org>
To: tgl@sss.pgh.pa.us
Cc: alvherre@kurilemu.de, ojford@gmail.com, peter@eisentraut.org,
 li.evan.chao@gmail.com, krasiyan@gmail.com, vik@postgresfriends.org,
 andrew@tao11.riddles.org.uk, david@fetter.org,
 pgsql-hackers@lists.postgresql.org
Subject: Re: Add RESPECT/IGNORE NULLS and FROM FIRST/LAST options
From: Tatsuo Ishii <ishii@postgresql.org>
In-Reply-To: <1694377.1759683105@sss.pgh.pa.us>
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	<1694377.1759683105@sss.pgh.pa.us>
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> will be exited this time.  But there's another thing that is
> confusing: the NN_NULL case certainly looks like it's expecting
> to exit the loop, but that "break" will only get out of the switch
> not the loop.

You mean "NN_NOTNULL" case?  if (notnull_offset >= notnull_relpos),
then following "while (notnull_offset < notnull_relpos)" does not
satisfy the continuous condition of the while loop and exits the loop.
I can add "goto" to explicitly exit the loop if we want.

> Moreover, the NN_NULL case looks like it'd fail
> to notice end-of-frame.  And it's not entirely clear what the
> default case thinks it's doing either.

WinGetFuncArgInPartition() does not care about frame, no?

> In short, this loop is impossible to understand, and the lack of
> comments doesn't help.  Even if it's not actually buggy, it
> needs to be rewritten in a way that helps readers and compilers
> see that it's not buggy.  I think it might help to separate the
> detection of null-ness and fetching of the datum value (if required)
> from the loop control logic.

Thanks for the idea.  Let me think if I could change the loop to be
easier to understand.

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