Re: Emitting JSON to file using COPY TO

On Tue, Jan 9, 2024 at 4:40 AM Joe Conway <mail@joeconway.com> wrote:
>
> On 1/8/24 14:36, Dean Rasheed wrote:
> > On Thu, 7 Dec 2023 at 01:10, Joe Conway <mail@joeconway.com> wrote:
> >>
> >> The attached should fix the CopyOut response to say one column.
> >>
> >
> > Playing around with this, I found a couple of cases that generate an error:
> >
> > COPY (SELECT 1 UNION ALL SELECT 2) TO stdout WITH (format json);
> >
> > COPY (VALUES (1), (2)) TO stdout WITH (format json);
> >
> > both of those generate the following:
> >
> > ERROR:  record type has not been registered
>
>
> Thanks -- will have a look
>
> --
> Joe Conway
> PostgreSQL Contributors Team
> RDS Open Source Databases
> Amazon Web Services: https://aws.amazon.com
>
>
>

In the function CopyOneRowTo, I try to call the function BlessTupleDesc again.

+BlessTupleDesc(slot->tts_tupleDescriptor);
rowdata = ExecFetchSlotHeapTupleDatum(slot);

Please check the attachment. (one test.sql file, one patch, one bless twice).

Now the error cases are gone, less cases return error.
but the new result is not the expected.

`COPY (SELECT g from generate_series(1,1) g) TO stdout WITH (format json);`
returns
{"":1}
The expected result would be `{"g":1}`.

I think the reason is maybe related to the function copy_dest_startup.