Обсуждение: tupdesc: simplify assert in equalTupleDescs()

Hi,

While reading the code, I saw these assertions in equalTupleDescs():
```
        CompactAttribute *cattr1 = TupleDescCompactAttr(tupdesc1, i);
        CompactAttribute *cattr2 = TupleDescCompactAttr(tupdesc2, i);

        Assert(cattr1->attnullability != ATTNULLABLE_UNKNOWN);
        Assert((cattr1->attnullability == ATTNULLABLE_UNKNOWN) ==
               (cattr2->attnullability == ATTNULLABLE_UNKNOWN));

```

The first assertion already guarantees that cattr1->attnullability is not ATTNULLABLE_UNKNOWN, so in the second one the
expressioncattr1->attnullability == ATTNULLABLE_UNKNOWN will always be false, That means the second assertion is
effectivelyjust checking that cattr2->attnullability is also not ATTNULLABLE_UNKNOWN. 

So the current code is correct, but it feels a bit harder to read than necessary. This patch just simplifies the second
assertionin a direct way. 

Best regards,
--
Chao Li (Evan)
HighGo Software Co., Ltd.
https://www.highgo.com/

Hi,

On Tue, 17 Mar 2026 at 10:22, Chao Li <li.evan.chao@gmail.com> wrote:
>
> While reading the code, I saw these assertions in equalTupleDescs():
> ```
>                 CompactAttribute *cattr1 = TupleDescCompactAttr(tupdesc1, i);
>                 CompactAttribute *cattr2 = TupleDescCompactAttr(tupdesc2, i);
>
>                 Assert(cattr1->attnullability != ATTNULLABLE_UNKNOWN);
>                 Assert((cattr1->attnullability == ATTNULLABLE_UNKNOWN) ==
>                            (cattr2->attnullability == ATTNULLABLE_UNKNOWN));
>
> ```
>
> The first assertion already guarantees that cattr1->attnullability is not ATTNULLABLE_UNKNOWN, so in the second one
theexpression cattr1->attnullability == ATTNULLABLE_UNKNOWN will always be false, That means the second assertion is
effectivelyjust checking that cattr2->attnullability is also not ATTNULLABLE_UNKNOWN. 
>
> So the current code is correct, but it feels a bit harder to read than necessary. This patch just simplifies the
secondassertion in a direct way. 

Thank you for the report! You are right and the patch looks good to me.

Nitpick: It is still a bit hard to understand why
'cattr2->attnullability' should not be equal to 'ATTNULLABLE_UNKNOWN'.
It would be good to add a comment explaining that 'attr2->attnotnull'
should be true too because 'if (attr1->attnotnull !=
attr2->attnotnull)' is returning false.

--
Regards,
Nazir Bilal Yavuz
Microsoft

> On Apr 29, 2026, at 02:29, surya poondla <suryapoondla4@gmail.com> wrote:
> 
> Hi Chao,
> 
> Thank you for working on this.
> 
> The patch looks good to me and makes the code more easy to read.
> 
> Regards,
> Surya Poondla

Thanks for your review.

Best regards,
--
Chao Li (Evan)
HighGo Software Co., Ltd.
https://www.highgo.com/