Re: Document NULL - Mailing list pgsql-hackers
| From | David G. Johnston |
|---|---|
| Subject | Re: Document NULL |
| Date | |
| Msg-id | CAKFQuwZ+AfKe76W+csw0mwxMC0EWwDC-triOgVF66xq5pSuJsw@mail.gmail.com Whole thread Raw |
| In response to | Re: Document NULL (Chao Li <li.evan.chao@gmail.com>) |
| List | pgsql-hackers |
On Fri, Nov 14, 2025 at 1:52 AM Chao Li <li.evan.chao@gmail.com> wrote:
> On Nov 11, 2025, at 23:34, Álvaro Herrera <alvherre@kurilemu.de> wrote:
>
> On 2025-Jun-18, David G. Johnston wrote:
>
>> Version 8.
>>
>> Marking this Ready to Commit in CF 2025-09 (CF PG19-1)
>
> I have rebased this; here's v9. I haven't reviewed it in depth, but
> intend to give it a read and get it pushed sometime in the
> not-too-distant future, so if anybody wants to review it some more, it'd
> be appreciated.
I just reviewed this patch and got some comments:
>
> Note that this rebase was across the func.sgml split, which means I had
> to do some "manual" merging. Looking at the git diff --stat output, it
> seems to match what was there before, so I don't think anything was
> lost.
Thanks for the review. Still on extended travel sabbatical until December so my full attention may not yet be here; and am not able to resubmit a new patch version right now. I'll do so in a couple of weeks, but appreciate any assistance given.
>
> --
> Álvaro Herrera Breisgau, Deutschland — https://www.EnterpriseDB.com/
> "Linux transformó mi computadora, de una `máquina para hacer cosas',
> en un aparato realmente entretenido, sobre el cual cada día aprendo
> algo nuevo" (Jaime Salinas)
> <v9-0001-doc-Add-an-overview-of-NULL-treatment-in-PostgreS.patch>
1 - func-comparsions.sgml
```
+ tests are AND'd together. Note that <literal>IS DISTINCT FROM</literal> is not an operator.
```
The “note that” sentence is not clear. I believe you meant to say the “IS DISTINCT FROM” cannot generate null values because it is not an operator. But one thing being not an operator doesn’t mean it cannot generate null value, right? So I think we’d be explicit, I am suggesting:
"Note that, IS DISTINCT FROM does not produce null results — it always returns true or false."
This comment applies to 2 occurrences.
Reading this again here, the first part where "operator cannot produce null values" seems sufficient and calling out "is distinct from" can probably just be removed instead of rephrased.
2 - func-comparsions.sgml
```
+ Each side is evaluated and they are compared row-wise.
+ As discussed and shown in <xref linkend="nullvalues-multielementcomparison-composite"/>,
+ null values are treated as being equal to other null values and greater
+ than all non-null values.
+ Composite type
comparisons are allowed when the <replaceable>operator</replaceable> is
```
The “composite type” line is too short, consider move the next line up.
Yeah, some of the lines are broken purely for review patch diff considerations.
For ANY, it should be “OR’d”.
I very well may have flipped the AND/ORs around.
8 - nullvalues.sgml
```
+ to any other value (e.g., <literal>IS DISTINCT</literal>, and <literal>IS TRUE</literal>.)
```
Should “IS DISTINCT” be “IS DISTINCT FROM”?
Probably.
9 - nullvalues.sgml
```
+ all non-null valueS.
```
Nit typo. Should be small “s".
Yeah.
David J.
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