Re: [patch] bit XOR aggregate functions

On 3/6/21 8:55 PM, David Fetter wrote:
> On Wed, Mar 03, 2021 at 03:30:15PM +0100, Peter Eisentraut wrote:
>> On 10.02.21 06:42, Kyotaro Horiguchi wrote:
>>> We already had CREATE AGGREATE at the time, so BIT_XOR can be
>>> thought as it falls into the same category with BIT_AND and
>>> BIT_OR, that is, we may have BIT_XOR as an intrinsic aggregation?
>>
>> I think the use of BIT_XOR is quite separate from BIT_AND and
>> BIT_OR. The latter give you an "all" or "any" result of the bits
>> set. BIT_XOR will return 1 or true if an odd number of inputs are 1
>> or true, which isn't useful by itself. But it can be used as a
>> checksum, so it seems pretty reasonable to me to add it. Perhaps
>> the use case could be pointed out in the documentation.
>
> If this is the only use case, is there some way to refuse to execute
> it if it doesn't contain an unambiguous ORDER BY, as illustrated
> below?
>
> 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?
--
Vik Fearing