Re: Add RESPECT/IGNORE NULLS and FROM FIRST/LAST options

Tatsuo Ishii <ishii@postgresql.org>

From: Tatsuo Ishii <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

Date: 2025-10-06T00:09:01Z

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 →

Fix coding style with "else".
- 20628b62e46e 19 (unreleased) landed
Fix multi WinGetFuncArgInFrame/Partition calls with IGNORE NULLS.
- 2d7b247cb414 19 (unreleased) landed
Fix Coverity issue reported in commit 2273fa32bce.
- dd766a441d69 19 (unreleased) landed
Use ereport rather than elog in WinCheckAndInitializeNullTreatment.
- 5f3808646f67 19 (unreleased) landed
Avoid uninitialized-variable warnings from older compilers.
- 71540dcdcb22 19 (unreleased) cited
Fix Coverity issues reported in commit 25a30bbd423.
- 2273fa32bce7 19 (unreleased) landed
Improve EXPLAIN's display of window functions.
- 8b1b342544b6 18.0 cited
Automatically generate node support functions
- 964d01ae90c3 16.0 cited

> 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