Re: COPY TO: provide hint when WHERE clause is used

On Sun, Aug 31, 2025 at 3:14 AM Jim Jones <jim(dot)jones(at)uni-muenster(dot)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.