Re: why generated columsn cannot be used in COPY TO?

On Fri, Oct 6, 2023 at 8:54 AM Adrian Klaver <adrian.klaver@aklaver.com> wrote:

On 10/6/23 08:45, Ron wrote:
> On 10/6/23 09:04, Andreas Kretschmer wrote:
>>

>>> Not sure how convincing that reasoning is, but it was at least
>>> thought about.  I do agree with it as far as the default column
>>> list goes, but maybe we could allow explicit selection of these
>>> columns in COPY TO.
>>
>> sounds okay
>
> Nah.  "The programmer -- and DBA -- on the Clapham omnibus" quite
> reasonably expects that COPY table_name TO (output)" copies all the
> columns listed in "\d table_name".
>

Yeah, I would agree.

Sure, but it doesn't.  Mainly since copy's original design was intended to solve the dump/restore problem and it doesn't make sense to specify data for inbound generated data.  So while we do have a POLA violation here the desirability to now fix it years later is basically zero.  And the current behavior is at least defensible and consistent.  And there is a very easy way to get the desired output making any change that much harder a sell.

The error message maybe could use some help though, and if there isn't a hint maybe add one.

David J.