| From: | Vik Fearing <vik(at)postgresfriends(dot)org> |
|---|---|
| To: | "David G(dot) Johnston" <david(dot)g(dot)johnston(at)gmail(dot)com>, David Fetter <david(at)fetter(dot)org> |
| Cc: | Peter Eisentraut <peter(dot)eisentraut(at)enterprisedb(dot)com>, Kyotaro Horiguchi <horikyota(dot)ntt(at)gmail(dot)com>, "bashtanov(at)imap(dot)cc" <bashtanov(at)imap(dot)cc>, "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: [patch] bit XOR aggregate functions |
| Date: | 2021-03-07 09:36:35 |
| Message-ID: | 8081ec73-c971-70c8-244f-242694d20ae8@postgresfriends.org |
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| Lists: | pgsql-hackers |
On 3/6/21 9:06 PM, David G. Johnston wrote:
> On Saturday, March 6, 2021, David Fetter <david(at)fetter(dot)org> wrote:
>
>>
>>>> SELECT BIT_XOR(b ORDER BY a, c)... /* works */
>>>> SELECT BIT_XOR(b) OVER (ORDER BY a, c)... /* works */
>>>> SELECT BIT_XOR(b) FROM... /* errors out */
>>>
>>>
>>> Why would such an error be necessary, or even desirable?
>>
>> Because there is no way to ensure that the results remain consistent
>> from one execution to the next without such a guarantee.
>>
>
> Numerous existing aggregate functions have this behavior. Making those
> error isn’t an option. So is making this a special case something we want
> to do (and also maybe make doing so the rule going forward)?
Aside from the fact that bit_xor() does not need this, I am opposed to
it in general. It is not our job to make people write correct queries.
--
Vik Fearing
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