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From: Nathan Bossart <nathandbossart@gmail.com>
To: Joe Conway <mail@joeconway.com>
Cc: Davin Shearer <davin@apache.org>
Cc: PostgreSQL-development <pgsql-hackers@postgreSQL.org>
Subject: Re: Emitting JSON to file using COPY TO
Date: Fri, 1 Dec 2023 17:09:58 -0600
Message-ID: <20231201230958.GA1786735@nathanxps13> (raw)
In-Reply-To: <24e3ee88-ec1e-421b-89ae-8a47ee0d2df1@joeconway.com>
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	<24e3ee88-ec1e-421b-89ae-8a47ee0d2df1@joeconway.com>

On Fri, Dec 01, 2023 at 02:28:55PM -0500, Joe Conway wrote:
> I did a quick PoC patch (attached) -- if there interest and no hard
> objections I would like to get it up to speed for the January commitfest.

Cool.  I would expect there to be interest, given all the other JSON
support that has been added thus far.

I noticed that, with the PoC patch, "json" is the only format that must be
quoted.  Without quotes, I see a syntax error.  I'm assuming there's a
conflict with another json-related rule somewhere in gram.y, but I haven't
tracked down exactly which one is causing it.

> 1. Is supporting JSON array format sufficient, or does it need to support
> some other options? How flexible does the support scheme need to be?

I don't presently have a strong opinion on this one.  My instinct would be
start with something simple, though.  I don't think we offer any special
options for log_destination...

> 2. This only supports COPY TO and we would undoubtedly want to support COPY
> FROM for JSON as well, but is that required from the start?

I would vote for including COPY FROM support from the start.

> ! 	if (!cstate->opts.json_mode)

I think it's unfortunate that this further complicates the branching in
CopyOneRowTo(), but after some quick glances at the code, I'm not sure it's
worth refactoring a bunch of stuff to make this nicer.

-- 
Nathan Bossart
Amazon Web Services: https://aws.amazon.com





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