Re: Proposition for autoname columns

On 11/12/20 9:14 AM, Eugen Konkov wrote:
> Hello Andrew,
>
> Thursday, November 12, 2020, 3:19:39 PM, you wrote:
>
>
>> On 11/11/20 7:55 PM, Bruce Momjian wrote:
>>> On Thu, Nov 12, 2020 at 12:18:49AM +0000, Dagfinn Ilmari Mannsåker wrote:
>>>> Bruce Momjian <bruce(at)momjian(dot)us> writes:
>>>>> I think we could do it, but it would only work if the column was output
>>>>> as a single json value, and not a multi-key/value field. I am afraid if
>>>>> we tried to do it, the result would be too inconsistent to be useful.
>>>> Could this be done via the support function, so that the top-level
>>>> operator/function in each select list item can return a suggested column
>>>> name if the relevant arguments are constants?
>>> Yes, the user explicitly calling a function would be much easier to
>>> predict.
>>>
>> I suspect this is doomed to failure. There is no guarantee that the path
>> expression is going to be static or constant across rows. Say you have
>> this table:
>> x: foo, j: {"foo": 1, "bar": 2}
>> x: bar  j: {"foo": 3, "bar": 4}
>> and you say:
>>   select j->>x from mytable;
>> What should the column be named?
> Suppose it should be named 'as x'

So if we then say:

select x, j->>x from mytable;

you want both result columns named x? That seems like a recipe for
serious confusion. I really don't think this proposal has been properly
thought through.

cheers

andrew

--
Andrew Dunstan
EDB: https://www.enterprisedb.com