Is there a reason why COPY TO STDOUT does not allow columns to be specified
more than once?

pei=# copy test1 (a, a) to stdout;
ERROR: 42701: column "a" specified more than once

Or is this just an overly extensive check that is actually intended for COPY
FROM STDIN?

--
Peter Eisentraut
http://developer.postgresql.org/~petere/

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Peter Eisentraut wrote:
> Is there a reason why COPY TO STDOUT does not allow columns to be specified
> more than once?
>
> pei=# copy test1 (a, a) to stdout;
> ERROR: 42701: column "a" specified more than once
>
> Or is this just an overly extensive check that is actually intended for COPY
> FROM STDIN?
>
>

You should be able to get around it with:

COPY (SELECT a , a FROM test1) TO stdout;

cheers

andew

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Hi,

> >
> > pei=# copy test1 (a, a) to stdout;
> > ERROR: 42701: column "a" specified more than once
> >
> > Or is this just an overly extensive check that is actually intended for
> COPY
> > FROM STDIN?
> >
> >
>

This seems to be a common check in both "COPY TO" and "COPY FROM" cases
source/destination being STDIN or otherwise. While it definitely makes sense
for the FROM case maybe we could relax this for the COPY TO case.

Regards,
Nikhils
--
EnterpriseDB http://www.enterprisedb.com

Peter Eisentraut <peter_e@gmx.net> writes:
> Is there a reason why COPY TO STDOUT does not allow columns to be specified
> more than once?

> pei=# copy test1 (a, a) to stdout;
> ERROR: 42701: column "a" specified more than once

> Or is this just an overly extensive check that is actually intended for COPY
> FROM STDIN?

I think it's reasonable even for COPY TO, since IMHO the odds that it's
a typo, rather than intentional, are probably 100:1.

As already noted, we do have a workaround if that is truly what you
intend.

regards, tom lane

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Am Donnerstag, 20. Dezember 2007 schrieb Tom Lane:
> I think it's reasonable even for COPY TO, since IMHO the odds that it's
> a typo, rather than intentional, are probably 100:1.

ISTM that with this line of argument we could disable thousands of valid uses
of SQL commands.

--
Peter Eisentraut
http://developer.postgresql.org/~petere/

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