From: | Sehrope Sarkuni <sehrope(at)jackdb(dot)com> |
---|---|
To: | Joe Conway <mail(at)joeconway(dot)com> |
Cc: | Andrew Dunstan <andrew(at)dunslane(dot)net>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Davin Shearer <davin(at)apache(dot)org>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: Emitting JSON to file using COPY TO |
Date: | 2023-12-06 21:42:11 |
Message-ID: | CAH7T-aow6jM-v1K462O7N=doOZxSD79zsH6prDCft7wv91F48A@mail.gmail.com |
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Lists: | pgsql-general pgsql-hackers |
On Wed, Dec 6, 2023 at 4:29 PM Joe Conway <mail(at)joeconway(dot)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/
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