čt 12. 11. 2020 v 16:59 odesílatel Andrew Dunstan <andrew@dunslane.net> napsal:
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@momjian.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.
Why? It is consistent - you will get a value of key x, and anybody expects, so value should be different.
