Re: COPY TO: provide hint when WHERE clause is used - Mailing list pgsql-hackers

From Atsushi Torikoshi
Subject Re: COPY TO: provide hint when WHERE clause is used
Date
Msg-id CAM6-o=DVOd-jpO6WparhuPjOG5QkNiyspdPzeOrDT6x_JAqDMw@mail.gmail.com
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In response to Re: COPY TO: provide hint when WHERE clause is used  (Jim Jones <jim.jones@uni-muenster.de>)
Responses Re: COPY TO: provide hint when WHERE clause is used
List pgsql-hackers


On Sun, Aug 31, 2025 at 3:14 AM Jim Jones <jim.jones@uni-muenster.de> wrote:
>
> Hi
>
> On 19.08.25 03:35, torikoshia wrote:
> > Considering what the user was trying to do, it might be helpful to
> > provide a similar hint in this case as well.
> > I’ve attached a patch that adds such a hint.
> >
> > What do you think?
> >
>
> +1
>
> I tested the patch and the error message now has the intended HINT ...
>
> postgres=# COPY t1 TO STDOUT WHERE i > 5;
> ERROR:  WHERE clause not allowed with COPY TO
> LINE 1: COPY t1 TO STDOUT WHERE i > 5;
>                           ^
> HINT:  Try the COPY (SELECT ... WHERE ...) TO variant.
>
> ... which aligns with the HINT from COPY TO from views
>
> postgres=# COPY v1 TO STDOUT;
> ERROR:  cannot copy from view "v1"
> HINT:  Try the COPY (SELECT ...) TO variant.

Thanks for your review!

Updated the patch to pass regression tests.
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