Re: Emitting JSON to file using COPY TO

On Wed, Dec 6, 2023 at 4:29 PM Joe Conway <mail@joeconway.com> wrote:

> > 1. Outputting a top level JSON object without the additional column
> > keys. IIUC, the top level keys are always the column names. A common use
> > case would be a single json/jsonb column that is already formatted
> > exactly as the user would like for output. Rather than enveloping it in
> > an object with a dedicated key, it would be nice to be able to output it
> > directly. This would allow non-object results to be outputted as well
> > (e.g., lines of JSON arrays, numbers, or strings). Due to how JSON is
> > structured, I think this would play nice with the JSON lines v.s. array
> > concept.
> >
> > COPY (SELECT json_build_object('foo', x) AS i_am_ignored FROM
> > generate_series(1, 3) x) TO STDOUT WITH (FORMAT JSON,
> > SOME_OPTION_TO_NOT_ENVELOPE)
> > {"foo":1}
> > {"foo":2}
> > {"foo":3}
>
> Your example does not match what you describe, or do I misunderstand? I
> thought your goal was to eliminate the repeated "foo" from each row...
>

The "foo" in this case is explicit as I'm adding it when building the
object. What I was trying to show was not adding an additional object
wrapper / envelope.

So each row is:

{"foo":1}

Rather than:

"{"json_build_object":{"foo":1}}

If each row has exactly one json / jsonb field, then the user has already
indicated the format for each row.

That same mechanism can be used to remove the "foo" entirely via a
json/jsonb array.

Regards,
-- Sehrope Sarkuni
Founder & CEO | JackDB, Inc. | https://www.jackdb.com/