Horton

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

Vik Fearing <vik@postgresfriends.org>

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From: Vik Fearing <vik@postgresfriends.org>
To: Oliver Ford <ojford@gmail.com>, Tatsuo Ishii <ishii@sraoss.co.jp>
Cc: Pg Hackers <pgsql-hackers@postgresql.org>, Tom Lane <tgl@sss.pgh.pa.us>, andrew@tao11.riddles.org.uk, David Fetter <david@fetter.org>, Krasiyan Andreev <krasiyan@gmail.com>
Date: 2024-09-08T13:22:13Z
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. Fix coding style with "else".

  2. Fix multi WinGetFuncArgInFrame/Partition calls with IGNORE NULLS.

  3. Fix Coverity issue reported in commit 2273fa32bce.

  4. Use ereport rather than elog in WinCheckAndInitializeNullTreatment.

  5. Avoid uninitialized-variable warnings from older compilers.

  6. Fix Coverity issues reported in commit 25a30bbd423.

  7. Improve EXPLAIN's display of window functions.

  8. Automatically generate node support functions

On 9/7/24 22:25, Oliver Ford wrote:
> On Sat, May 6, 2023 at 9:41 AM Oliver Ford <ojford@gmail.com> wrote:
>>
>>
>>
>> On Sat, 6 May 2023, 04:57 Tatsuo Ishii, <ishii@sraoss.co.jp> wrote:
>>>
>>> Attached is the patch to implement this (on top of your patch).
>>>
>>> test=# SELECT row_number() RESPECT NULLS OVER () FROM (SELECT 1) AS s;
>>> ERROR:  window function row_number cannot have RESPECT NULLS or IGNORE NULLS
>>
>>
>> The last time this was discussed (https://www.postgresql.org/message-id/1037735.1610402426%40sss.pgh.pa.us) it was suggested to make the feature generalizable, beyond what the standard says it should be limited to.
>>
>> With it generalizable, there would need to be extra checks for custom functions, such as if they allow multiple column arguments (which I'll add in v2 of the patch if the design's accepted).
>>
>> So I think we need a consensus on whether to stick to limiting it to several specific functions, or making it generalized yet agreeing the rules to limit it (such as no agg functions, and no functions with multiple column arguments).
> 
> Reviving this thread, I've attached a rebased patch with code, docs,
> and tests and added it to November commitfest.

Excellent!  One of these days we'll get this in. :-)

I have a problem with this test, though:

     SELECT sum(orbit) RESPECT NULLS OVER () FROM planets; -- succeeds

Why should that succeed?  Especially since aggregates such as SUM() will 
ignore nulls!  The error message on its partner seems to confirm this:

     SELECT sum(orbit) IGNORE NULLS OVER () FROM planets; -- fails
     ERROR:  aggregate functions do not accept RESPECT/IGNORE NULLS

I believe they should both fail.
-- 
Vik Fearing