From: | Andrew Dunstan <andrew(at)dunslane(dot)net> |
---|---|
To: | Eugen Konkov <kes-kes(at)yandex(dot)ru>, Bruce Momjian <bruce(at)momjian(dot)us>, Dagfinn Ilmari Mannsåker <ilmari(at)ilmari(dot)org> |
Cc: | pgsql-hackers(at)postgresql(dot)org |
Subject: | Re: Proposition for autoname columns |
Date: | 2020-11-12 15:58:51 |
Message-ID: | e94ec7da-1379-9c40-be4c-df42edd0f6f9@dunslane.net |
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Lists: | pgsql-hackers |
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
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